Fix SD-JWT examples; add detail to the 'Securing Verifiable Credentia…

…ls' section (#304)

* fix sd-jwt examples

* securing text clarificaiton

* formatting

* Update index.html

Co-authored-by: Ted Thibodeau Jr <[email protected]>

* merge

* revert media types

* Apply suggestions from code review

Co-authored-by: Ted Thibodeau Jr <[email protected]>

* Update index.html

Co-authored-by: Michael B. Jones <[email protected]>

* Update index.html

Co-authored-by: Michael B. Jones <[email protected]>

* Apply suggestions from code review

Co-authored-by: Michael B. Jones <[email protected]>

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Co-authored-by: Ted Thibodeau Jr <[email protected]>
Co-authored-by: Michael B. Jones <[email protected]>