PEP 678: Convert footnotes to inline links

Per python#2302.

pep-0678.rst

@@ -115,15 +115,16 @@ includes a note of the minimal failing example::
 Non-goals
 ---------
 ``__note__`` is *not* intended to carry structured data.  If your note is for
-use by a program rather than display to a human, we recommend instead (or
-additionally) choosing a convention for an attribute like e.g.
-``err._parse_errors = ...`` on the error or ``ExceptionGroup`` [1]_ [2]_
+use by a program rather than display to a human, `we recommend
+<https://discuss.python.org/t/accepting-pep-654-exception-groups-and-except/10813/26>`__
+instead (or additionally) choosing a convention for an attribute like e.g.
+``err._parse_errors = ...`` on the error or ``ExceptionGroup``.
 
 As a rule of thumb, prefer `exception chaining
 <https://docs.python.org/3/tutorial/errors.html#exception-chaining>`__ when the
 error is going to be re-raised or handled as an individual error, and prefer
 ``__note__`` when you are collecting multiple exception objects to handle
-together or later. [3]_
+together or later. [1]_
 
 
 Specification
@@ -149,8 +150,9 @@ Backwards Compatibility
 =======================
 
 System-defined or "dunder" names (following the pattern ``__*__``) are part of
-the language specification, with unassigned names reserved for future use and
-subject to breakage without warning [4]_.
+the language specification, with `unassigned names reserved for future use and
+subject to breakage without warning
+<https://docs.python.org/3/reference/lexical_analysis.html#reserved-classes-of-identifiers>`__.
 
 We are also unaware of any code which *would* be broken by adding ``__note__``;
 assigning to a ``.__note__`` attribute already *works* on current versions of
@@ -163,17 +165,17 @@ How to Teach This
 =================
 
 The ``__note__`` attribute will be documented as part of the language standard,
-and explained as part of the tutorial "Errors and Exceptions" [5]_.
-
+and explained as part of `the "Errors and Exceptions" tutorial
+<https://github.com/python/cpython/pull/30441>`__.
 
 
 Reference Implementation
 ========================
 
-``BaseException.__note__`` was implemented in [6]_ and released in CPython
-3.11.0a3, following discussions related to :pep:`654`. [7]_ [8]_ [9]_
-
+``BaseException.__note__`` was `implemented in <https://github.com/python/cpython/pull/29880>`__ and released in CPython
+3.11.0a3, following discussions related to :pep:`654`. [2]_
 
+https://bugs.python.org/issue45607
 
 Rejected Ideas
 ==============
@@ -204,8 +206,9 @@ for downstream code.  We consider *always* raising a ``Wrapper`` exception
 unacceptably inelegant; but because custom exception types might have any
 number of required arguments we can't always create an instance of the *same*
 type with our explanation. In cases where the exact exception type is known
-this can work, such as the standard library ``http.client`` code [10]_, but not
-for libraries which call user code.
+this can work, such as the standard library ``http.client`` `code
+<https://github.com/python/cpython/blob/69ef1b59983065ddb0b712dac3b04107c5059735/Lib/http/client.py#L596-L597>`__,
+but not for libraries which call user code.
 
 Second, exception chaining reports several lines of additional detail, which
 are distracting for experienced users and can be very confusing for beginners.
@@ -297,9 +300,11 @@ formatted for display after propagation.
 
 Add a helper function ``contextlib.add_exc_note()``
 ---------------------------------------------------
-It was suggested [11]_ that we add a utility such as the one below to the
-standard library. We are open to this idea, but do not see it as a core part of
-the proposal of this PEP as it can be added as an enhancement later.
+It `was suggested
+<https://www.reddit.com/r/Python/comments/rmrvxv/pep_678_enriching_exceptions_with_notes/hptbul1/>`__
+that we add a utility such as the one below to the standard library. We are
+open to this idea, but do not see it as a core part of the proposal of this PEP
+as it can be added as an enhancement later.
 
 .. code-block:: python
 
@@ -329,19 +334,12 @@ justifies new language syntax.
 References
 ==========
 
-.. [1] https://discuss.python.org/t/accepting-pep-654-exception-groups-and-except/10813/26
-.. [2] https://bugs.python.org/issue46431
-.. [3] this principle was established in the 2003 mail thread which led to :pep:`3134`,
+.. [1] this principle was established in the 2003 mail thread which led to :pep:`3134`,
        and included a proposal for a group-of-exceptions type!
        https://mail.python.org/pipermail/python-dev/2003-January/032492.html
-.. [4] https://docs.python.org/3/reference/lexical_analysis.html#reserved-classes-of-identifiers
-.. [5] https://github.com/python/cpython/pull/30441
-.. [6] https://github.com/python/cpython/pull/29880
-.. [7] https://discuss.python.org/t/accepting-pep-654-exception-groups-and-except/10813/9
-.. [8] https://github.com/python/cpython/pull/28569#discussion_r721768348
-.. [9] https://bugs.python.org/issue45607
-.. [10] https://github.com/python/cpython/blob/69ef1b59983065ddb0b712dac3b04107c5059735/Lib/http/client.py#L596-L597
-.. [11] https://www.reddit.com/r/Python/comments/rmrvxv/pep_678_enriching_exceptions_with_notes/hptbul1/
+.. [2] particularly those at https://bugs.python.org/issue45607,
+       https://discuss.python.org/t/accepting-pep-654-exception-groups-and-except/10813/9,
+       https://github.com/python/cpython/pull/28569#discussion_r721768348, and