Consider removing `workspaceContains` activation event

**Is your feature request related to a problem? Please describe.**

This extension will eagerly activate if I have any workflow files in my repo... even if I don't intend to do any work on GitHub Actions in my repo.

This is because this extension has the following activation event:
https://github.com/github/vscode-github-actions/blob/main/package.json#L28

**Describe the solution you'd like**

Remove this activation event. Your extension will already activate when one of your views open or when you open a workflow file thanks to your [registering of a language](https://github.com/github/vscode-github-actions/blob/main/package.json#L40-L41). This should be sufficient. If it's not, I'm curious to know why.

**Additional context**

Activating eagerly affects other extensions running in the extension host and the ideal situation is that only extensions that are absolutely needed are activated. This keeps VS Code & the extension host lean and fast.

Inspect package.json around the workspaceContains activation event at line 28, along with the view and language registrations around lines 40–41. Remove the eager activation entry and verify that the extension still activates when one of its views opens or a workflow file is opened.

Scritto dal modello di indicizzazione a partire dal testo della issue.