Add 1.3.6 changelog, test IEEE P1363 sigs in DSSE

[haydentherapper]

Summary

Release Note

Documentation

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 48.93%. Comparing base (488eb97) to head (c35b193). Report is 72 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2063 +/- ## =========================================== - Coverage 66.46% 48.93% -17.53% =========================================== Files 92 80 -12 Lines 9258 6641 -2617 =========================================== - Hits 6153 3250 -2903 - Misses 2359 2987 +628 + Partials 746 404 -342 ``` | [Flag](https://app.codecov.io/gh/sigstore/rekor/pull/2063/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sigstore) | Coverage Δ | | |---|---|---| | [e2etests](https://app.codecov.io/gh/sigstore/rekor/pull/2063/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sigstore) | `?` | | | [unittests](https://app.codecov.io/gh/sigstore/rekor/pull/2063/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sigstore) | `48.93% <ø> (+1.25%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sigstore#carryforward-flags-in-the-pull-request-comment) to find out more.

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[haydentherapper]

Ideally would like to add a test for IEEE P1363 sigs too, will look at doing later. I've verified locally that it works though.

[haydentherapper]

Rebased and added a test