docs: PR preview (#194)

## 📜 Description

Added an ability to preview PRs.

## 💡 Motivation and Context

Sometimes it's easier to review PR when it's deployed (check how it
looks on mobile devices etc.).

The list below is important to take into consideration when PR will be
merged:

- don't remove pr-review directory in main deployment pipeline
- remove preview when PR was closed/merged (.nojekyl?)
- be sure that there is no race condition, when PR is getting merged

## 📢 Changelog

### CI
- added new job which deploys preview to github pages;

### Docs
- conditionally change `baseUrl` to handle case for previews;

## 🤔 How Has This Been Tested?

Tested using GitHub actions.

## 📝 Checklist

- [x] CI successfully passed

.github/workflows/verify-docs.yml

@@ -7,6 +7,11 @@ on:
     paths:
       - '.github/workflows/verify-docs.yml'
       - 'docs/**'
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - closed
 
 jobs:
   build:
@@ -41,3 +46,24 @@ jobs:
         run: yarn install --frozen-lockfile
       - name: Run Lint
         run: yarn markdownlint-cli2 "**/*.md" "#node_modules"
+  preview:
+    runs-on: ubuntu-latest
+    name: 🛫 Deploy preview
+    defaults:
+      run:
+        working-directory: docs
+    steps:
+      - uses: actions/checkout@v3
+      - run: echo "PREVIEW_PATH=pr-preview/pr-${{ github.event.number }}" >> "$GITHUB_ENV"
+      - uses: actions/setup-node@v3
+        with:
+          node-version: 16.x
+          cache: yarn
+      - name: Install dependencies
+        run: yarn install --frozen-lockfile
+      - name: Build website
+        run: yarn build
+      - name: Deploy preview
+        uses: rossjrw/pr-preview-action@v1
+        with:
+          source-dir: ./docs/build/

docs/docusaurus.config.js

@@ -4,12 +4,15 @@
 const lightCodeTheme = require('prism-react-renderer/themes/github');
 const darkCodeTheme = require('prism-react-renderer/themes/dracula');
 
+let baseUrl = '/react-native-keyboard-controller/';
+if (process.env.PREVIEW_PATH) baseUrl += process.env.PREVIEW_PATH;
+
 /** @type {import('@docusaurus/types').Config} */
 const config = {
   title: 'Keyboard Controller',
   tagline: 'Control each frame of keyboard movement in react native',
   url: 'https://kirillzyusko.github.io',
-  baseUrl: '/react-native-keyboard-controller/',
+  baseUrl: baseUrl,
   onBrokenLinks: 'throw',
   onBrokenMarkdownLinks: 'warn',
   favicon: 'img/favicon.ico',