fix(CI): roll our own linter for YAML (apache#3196)

Due to the ASF's policies changing we cannot use the original GitHub Actions for linting as they are not approved

Lint Markdown for rules:
- MD012/no-multiple-blanks
- MD032/blanks-around-lists

.github/ISSUE_TEMPLATE/bug.md

@@ -9,20 +9,18 @@ assignees: ''
 
 ### Issue description
 
-
 ### Environment
 
 * apisix version (cmd: `apisix version`):
 * OS: (cmd: `uname -a`)
 * OpenResty / Nginx version: (cmd: `nginx -V` or `openresty -V`)
 
 ### Minimal test code / Steps to reproduce the issue
+
 1.
 2.
 3.
 
 ### What's the actual result? (including assertion message & call stack if applicable)
 
-
-
 ### What's the expected result?

.github/ISSUE_TEMPLATE/request-help.md

@@ -9,7 +9,6 @@ assignees: ''
 
 ### Issue description
 
-
 ### Environment
 
 * apisix version (cmd: `apisix version`):

.github/workflows/lint.yml

@@ -19,5 +19,14 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+        with:
+          python-version: '3.x'  # Version range or exact version of a Python version to use, using SemVer's version range syntax
+          architecture: 'x64'  # optional x64 or x86. Defaults to x64 if not specified
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install yamllint
       - name: 🧹 YAML Lint
-        uses: ibiqlik/action-yamllint@v3
+        run: |
+          yamllint .

doc/plugins/openid-connect.md

@@ -80,7 +80,6 @@ will be rejected without redirecting to the ID provider to obtain a valid token.
 The method used to authenticate a request also affects the headers that can be enforced on the request before
 sending it to upstream. The headers that can be enforced are mentioned below in each relevant section.
 
-
 ### Token Introspection
 
 Token introspection helps to validate a request by verifying the token against an Oauth 2 authorization server.