Extract .pot file from translations

.github/workflows/l10n.yml

@@ -0,0 +1,19 @@
+name: L10n
+on: pull_request
+
+jobs:
+  l10n-extract-check:
+    runs-on: ubuntu-latest
+    name: Pot check
+    steps:
+    - uses: actions/checkout@master
+    - name: Set up Node
+      uses: actions/setup-node@v1
+      with:
+        node-version: 12.x
+    - name: npm install
+      run: npm ci
+    - name: extract l10n files
+      run: npm run l10n:extract
+    - name: Check l10n file changes
+      run: bash -c "[[ ! \"`git status --porcelain l10n`\" ]] || ( echo 'Uncommited l10n changes. Run `npm l10n:extract`.' && git status && exit 1 )"

build/extract-l10n.js

@@ -20,6 +20,6 @@ extractor
     ])
     .parseFilesGlob('./lib/**/*.@(ts|js)');
 
-extractor.savePotFile('./messages.pot');
+extractor.savePotFile('./l10n/messages.pot');
 
 extractor.printStats();

l10n/messages.pot

@@ -0,0 +1,3 @@
+msgid ""
+msgstr ""
+"Content-Type: text/plain; charset=UTF-8\n"

package.json

@@ -8,8 +8,8 @@
     "build": "babel ./lib --out-dir dist --extensions '.ts,.tsx' --source-maps && tsc --emitDeclarationOnly",
     "build:doc": "typedoc --excludeNotExported --mode file --out dist/doc lib/index.ts && touch dist/doc/.nojekyll",
     "check-types": "tsc",
-    "extract-l10n": "node build/extract-l10n.js",
     "dev": "babel ./lib --out-dir dist --extensions '.ts,.tsx' --watch",
+    "l10n:extract": "node build/extract-l10n.js",
     "test": "jest",
     "test:watch": "jest --watchAll"
   },