Restart the effort to turn GitGitGadget's core logic into a GitHub Action

In preparation for a different approach, remove what had been done in
5e0129b (Merge pull request #1055 from webstech/action, 2022-07-20)

I would like to go into a different direction:

- move pretty much all the core logic from `misc-helper` to `CIHelper`.

- use `ncc` to bundle `CIHelper` as a single `dist/index.js` file.

- add dedicates GitHub Actions in subdirectories that contain really
  small `index.js` files which in turn import the `CIHelper` and then
  let it do its magic.

As a consequence, the Azure Pipelines we currently use can then be
migrated to GitHub workflows in gitgitgadget/gitgitgadget-workflows and
use the Actions like this:

  - uses: gitgitgadget/gitgitgadget/handle-slash-command@v1
    with:
      repository: gitgitgadget/git
      pr-number: ...
      issue-comment-id: ...
      gitgitgadget-app-id: ${{ secrets.GITGITGADGET_GITHUB_APP_ID }}
      gitgitgadget-private-key: ${{ secrets.GITGITGADGET_GITHUB_APP_PRIVATE_KEY }}
      gitgitgadget-git-app-id: ${{ secrets.GITGITGADGET_GIT_GITHUB_APP_ID }}
      gitgitgadget-git-private-key: ${{ secrets.GITGITGADGET_GIT_GITHUB_APP_PRIVATE_KEY }}

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

.gitignore

@@ -10,4 +10,3 @@
 /obj/**
 /*.sln*
 /*.njsproj*
-/*.tgz

lib/misc-action.ts

@@ -25,9 +25,6 @@
     "url": "https://github.com/gitgitgadget/gitgitgadget/issues"
   },
   "homepage": "https://gitgitgadget.github.io/",
-  "files": [
-    "lib/*.ts"
-  ],
   "jest": {
     "extensionsToTreatAsEsm": [
       ".ts"