feat(): add support for github provided jwt auth (#257)

* fix: update `privateKeyRaw` condition

* fix: add `contents: read` permission

* fix: get token via `@actions/core`

- Update README
- Switch to use `getIDToken` method for Github token retrieval
- Bump `@actions/core` to 1.6.0
- Add `jwtGithubAudience` input
- Remove unnecessary code

* fix: add description for `jwtGithubAudience`

* fix: move default value for `jwtGithubAudience` to `action.yml`

* docs: fix typo in README & grammar

* test: add tests

* fix: reset `dist/index.js`

* fix: remove default value for `jwtGithubAudience` from `action.yml`

* fix: reset `dist/index.js`

* fix: reset `dist/index.js`

action.yml

@@ -69,6 +69,9 @@ inputs:
   jwtKeyPassword:
     description: 'Password for key stored in jwtPrivateKey (if needed)'
     required: false
+  jwtGithubAudience:
+    description: 'Identifies the recipient ("aud" claim) that the JWT is intended for'
+    required: false
   jwtTtl:
     description: 'Time in seconds, after which token expires'
     required: false