Move API Reference (#23777)

* merge mattermost-api-reference unchanged

* api: update repostiory paths

* api: drop GitPod for api (for now)

* api: improved node_modules target

* api: relocate GitHub actions to root

* Update .github/workflows/api.yml

Co-authored-by: Antonis Stamatiou <stamatiou.antonis@gmail.com>

* fix cache-dependency-path

* adopt node-version-file

* pin versions for uses

* tidy steps/runs

* api/.gitpod.yml: tidy

* api: rm now unused .gitlab-ci.yml

---------

Co-authored-by: Antonis Stamatiou <stamatiou.antonis@gmail.com>

.github/workflows/api.yml

@@ -0,0 +1,35 @@
+name: API
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: ./api
+
+    steps:
+    - name: Checkout code
+      uses: actions/checkout@ac593985615ec2ede58e132d2e21d2b1cbd6127c # v3.3.0
+
+    - uses: actions/setup-node@64ed1c7eab4cce3362f8c340dee64e5eaeef8f7c # v3.6.0
+      with:
+        node-version-file: .nvmrc
+        cache: 'npm'
+        cache-dependency-path: api/package-lock.json
+
+    - name: Run build
+      run: make build
+
+    - uses: actions/upload-artifact@0b7f8abb1508181956e8e162db84b466c27e18ce # v3.1.2
+      with:
+        name: mattermost-api-reference
+        path: api/v4/html