fix(credential-ld): let verifiers use all supported verification methods

[mirceanis]

What issue is this PR fixing

fixes #1329

What is being changed

The VeramoLdSignature.getSupportedVerificationType() can now return string[] as well as string This allows VeramoLdSignature suite implementations to signal compatibility with multiple Verification Method types for verification.

Quality

Check all that apply:

• [X] I want these changes to be integrated
• [X] I successfully ran pnpm i, pnpm build, pnpm test, pnpm test:browser locally.
• [X] I allow my PR to be updated by the reviewers (to speed up the review process).
• [ ] I added unit tests.
• [ ] I added integration tests.
• [X] I did not add automated tests because _____, and I am aware that a PR without tests will likely get rejected.

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (7896cea) 89.83% compared to head (cde68aa) 89.83%.

Files	Patch %	Lines
...s/credential-ld/src/suites/JsonWebSignature2020.ts	66.66%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## next #1331 +/- ## ======================================= Coverage 89.83% 89.83% ======================================= Files 176 176 Lines 27010 27017 +7 Branches 2120 2124 +4 ======================================= + Hits 24265 24272 +7 Misses 2745 2745 ```

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