Add i18n system

.github/workflows/ci-otapi3.yml

@@ -33,6 +33,9 @@ jobs:
         with:
           dotnet-version: '6.0.100'
 
+      - name: Install msgfmt
+        run: sudo apt-get install -y gettext
+
       - name: Produce build
         run: |
             cd TShockLauncher

.github/workflows/i18n-extract.yml

@@ -0,0 +1,23 @@
+name: i18n extraction
+on:
+  push:
+    branches: [ general-devel ]
+jobs:
+  extract:
+    runs-on: ubuntu-latest
+    env:
+      GITHUB_TOKEN: '${{ secrets.GITHUB_TOKEN }}'
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          submodules: 'recursive'
+
+      - uses: actions/setup-dotnet@v3
+        with:
+          dotnet-version: | 
+            3.1.x
+            6.0.100
+
+      - name: Run i18n checking/extraction script
+        run: ./.github/scripts/i18n.sh
+        shell: bash