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`

integrationTests/basic/rsa_keys.js

@@ -72,6 +72,7 @@ f52E9W2iFNt3sxB0KFtOkbkCAwEAAQ==
 `;
 
 module.exports = {
+    privateRsaKey,
     privateRsaKeyBase64,
     publicRsaKey
 };