Add CI setup & specify missing dependencies

[LinqLover]

Changelog:

• Add GitHub Action workflow (.github/workflows/main.yml) to run tests using smalltalkCI (.smalltalk.ston)
• Make integration tests CI-ready by providing:
  • secret variables for bot and client (they also have been defined in the repository settings)
  • a test database for TelegramClient (see assets/tests/tdlib.zip.gpg) that works out of the box without using a new authentication code. It is encrypted using another secret variable.
  • revising the TelegramBotIntegrationTest running logic to make it more robust and fail-safe
• Fix baseline and specify missing dependencies
  • Create an extra package (TelegramBot-Support-ShoutAttribute) for extensions depending on the not-yet-released ShoutAttribute changeset (4680c53)
  • Add BaselineOfTelegramBot >> #installPreviewDependencies to install other not-yet-released proposals for the Squeak Trunk (works around Add baseline reference to a changeset file? Metacello/metacello#528 and Merge versions from a baseline Metacello/metacello#530)
  • Depend on fork of TelegramClient until Display unsupported messages correctly hpi-swa-teaching/TelegramClient#311, Update versioning information for dependencies, baseline & CI hpi-swa-teaching/TelegramClient#312 have been merged (528ae9a)
  • Add missing and remove superfluous extension methods
• API: Revise offset computation for getUpdates method (89c79a0)
• Fix TelegramBotRequest >> #testSendAudio (305755e)
• Add badges to README.md (7621356)