Doc label check

A GitHub Action that checks whether the doc label is correct and comment in pull request.

How it works

doc label check automatically detects task lists in the description of an issue or a pull request and adds labels based on their states (checked or unchecked).

<!-- pull_request_template.md -->
### Documentation

Check the box below and label this PR (if you have committer privilege).

Need to update docs? 

- [ ] `doc-required` 
  
  (If you need help on updating docs, create a doc issue)
  
- [x] `no-need-doc` 
  
  (Please explain why)
  
- [ ] `doc` 
  
  (If this PR contains doc changes)

This description makes `auto-labeling` add `no-need-doc`. If someone updates the description as follows:

```markdown
### Documentation

Check the box below and label this PR (if you have committer privilege).

Need to update docs? 

- [x] `doc-required` 
  
  (If you need help on updating docs, create a doc issue)
  
- [ ] `no-need-doc` 
  
  (Please explain why)
  
- [ ] `doc` 
  
  (If this PR contains doc changes)

Then, `auto-labeling` removes `no-need-doc` and adds `doc-required`. **Note that unregistered labels are ignored.**

## Example workflow

```yml
name: Auto Labeling

on:
  pull_request:
    types:
      - opened
      - edited
      - labeled

# A GitHub token created for a PR coming from a fork doesn't have
# 'admin' or 'write' permission (which is required to add labels)
# To avoid this issue, you can use the `scheduled` event and run
# this action on a certain interval.
on:
  schedule:
    - cron: '*/10 * * * *'

jobs:
  labeling:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v2

      - uses: harupy/auto-labeling@master
        with:
          github-token: ${{ secrets.GITHUB_TOKEN }}
          label-pattern: '- \[(.*?)\] ?`(.+?)`' # matches '- [x] `label`'
          botname: 'pr-bot-test'

Inputs

inputs:
  github-token:
    description: 'GitHub token'
    required: true

  label-pattern:
    description: >
      Pattern (regular expression) to extract label states and names (e.g. '- \[(.*?)\] ?`(.+?)`').
    required: true
  
  bot-name: 
    description: The bot name
    required:true

  offset:
    description: >
      Only issues and pull requests updated at or after this offset (from the current time) will be labeled.
      Required only when running this action on the schedule event.
    required: false
    default: '1m' # means one month

  quiet:
    description: >
      Suppress logging output. Must be either "true" or "false"
    required: false
    default: 'false'