Update to 21w19a and Java 16

This commit can be used as an example on how to update your mod to Java 16. You will need to ensure you have Java 16 installed and set as the active version to run this.

Gradle 7 is required along with loom 0.8

.github/workflows/build.yml

@@ -12,9 +12,7 @@ jobs:
       matrix:
         # Use these Java versions
         java: [
-          1.8,  # Minimum supported by Minecraft
-          11,   # Current Java LTS
-          15    # Latest version
+          16    # Minimum supported by Minecraft
         ]
         # and run on both Linux and Windows
         os: [ubuntu-20.04, windows-latest]
@@ -34,7 +32,7 @@ jobs:
       - name: build
         run: ./gradlew build
       - name: capture build artifacts
-        if: ${{ runner.os == 'Linux' && matrix.java == '11' }} # Only upload artifacts built from LTS java on one OS
+        if: ${{ runner.os == 'Linux' && matrix.java == '16' }} # Only upload artifacts built from latest java on one OS
         uses: actions/upload-artifact@v2
         with:
           name: Artifacts