Add option to trigger workflow when the workflow file or it's dependent workflows are modified

[Gussy]

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The problem

For all the workflows we create, the below boilerplate almost always needs to be included, so that updating the workflow itself triggers the workflow (to test it before merging).

on:
  pull_request:
    paths:
      - '.github/workflows/build.yml'
      - 'dir/**'

For more complex workflows that rely on multiple composite workflows and calls other workflows, we end up with something verbose like below.

on:
  pull_request:
    paths:
      - '.github/actions/composite-action-a/**'
      - '.github/actions/composite-action-b/**'
      - '.github/actions/composite-action-c/**'
      - '.github/workflows/sub-workflow-a.yml'
      - '.github/workflows/sub-workflow-b.yml'
      - '.github/workflows/build.yml'
      - 'dir/**'
  push:
    branches:
      - main
    paths:
      - '.github/actions/composite-action-a/**'
      - '.github/actions/composite-action-b/**'
      - '.github/actions/composite-action-c/**'
      - '.github/workflows/sub-workflow-a.yml'
      - '.github/workflows/sub-workflow-b.yml'
      - '.github/workflows/build.yml'
      - 'dir/**'

Discovering and tracking these dependancies takes time and is error prone, especially if sub-workflow-*.yml call other composite actions themselves.

Feature Request

Add an on: workflow_modify trigger a workflow if it's own yml is changed, or any of it's dependent workflow yml files change.

For example, to trigger the workflow when it's own yml is changed

on:
  workflow_modify: self

Or to trigger the workflow when itself or any dependent yml files are changed

on:
  workflow_modify: all