Add license and README, document GIF cape + backend integration, cache CI

.gitea/workflows/build.yml

@@ -14,6 +14,7 @@ jobs:
         with:
           distribution: temurin
           java-version: '21'
+          cache: gradle
       - run: chmod +x ./gradlew
       - run: ./gradlew build --no-daemon
       - uses: actions/upload-artifact@v3

.gitea/workflows/release.yml

@@ -13,6 +13,7 @@ jobs:
         with:
           distribution: temurin
           java-version: '21'
+          cache: gradle
       - run: chmod +x ./gradlew
       - run: ./gradlew build --no-daemon
       - uses: akkuman/gitea-release-action@v1