ci: Add a typos check (#799)

This can be run locally by installing `typos` from
<https://github.com/crate-ci/typos>.

Configuration is in `.typos.toml`.

.github/workflows/ci.yaml

@@ -90,3 +90,12 @@ jobs:
       - uses: taiki-e/install-action@nextest
 
       - run: ci/nextest-compat.sh
+
+  # If this fails, consider changing your text or adding something to .typos.toml
+  typos:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: check typos
+        uses: crate-ci/[email protected]

.typos.toml

@@ -0,0 +1,22 @@
+# See the configuration reference at
+# https://github.com/crate-ci/typos/blob/master/docs/reference.md
+
+# Corrections take the form of a key/value pair. The key is the incorrect word
+# and the value is the correct word. If the key and value are the same, the
+# word is treated as always correct. If the value is an empty string, the word
+# is treated as always incorrect.
+
+# Match Identifier - Case Sensitive
+[default.extend-identifiers]
+Nd = "Nd"
+thr = "thr"
+
+# Match Inside a Word - Case Insensitive
+[default.extend-words]
+
+[files]
+# Include .github, .cargo, etc.
+ignore-hidden = false
+# /.git isn't in .gitignore, because git never tracks it.
+# Typos doesn't know that, though.
+extend-exclude = ["/.git"]