Improve github build infra (#18)

Make github action that should produce installable repos

.github/workflows/github_release.yml

@@ -0,0 +1,26 @@
+name: Make draft release
+
+on:
+  workflow_dispatch:
+
+jobs:
+  jpackage:
+    name: Run JPackage
+    uses: ./.github/workflows/jpackage.yml
+
+  release:
+    needs: jpackage
+    permissions:
+      contents: write
+    runs-on: ubuntu-latest
+    steps:
+
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - uses: actions/download-artifact@v4
+
+      - name: Release
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: gh release create --draft ${{ github.ref_name }} --title ${{ github.ref_name }} build/*.jar

.github/workflows/jpackage.yml

@@ -0,0 +1,40 @@
+name: Java CI with Gradle
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+  workflow_dispatch:
+  workflow_call:
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+
+    - uses: actions/checkout@v4
+
+    - name: Set up JDK 17 # TODO: check Java version
+      uses: actions/setup-java@v4
+      with:
+        java-version: '17'
+        distribution: 'temurin'
+
+    - name: Validate Gradle wrapper
+      uses: gradle/wrapper-validation-action@v2
+
+    - name: Build with Gradle
+      uses: gradle/gradle-build-action@v3
+      with:
+        arguments: build
+
+    - uses: actions/upload-artifact@v4
+      with:
+        path: build/libs/*.jar
+        name: build
+        retention-days: 7

README.md

@@ -94,6 +94,34 @@ Add a license file to your GitHub repo so that others know what they can and can
 
 This should be compatible with QuPath's license -- see https://github.com/qupath/qupath
 
+## Repository configuration
+
+### Easy install
+
+If you follow some conventions in naming your extension and making releases, then other QuPath users will find it easy to automatically
+install and update your extension!
+
+First, we suggest you name your extension `qupath-extension-[something]`, and keep it in its own repository (named the same as the extension),
+separate from other projects.
+
+Next, when you want to publish a new version of your extension, use the `github_release.yml` workflow included in this repository.
+
+To do so, you'd need to navigate to `Actions -> Make draft release -> Run workflow -> Run workflow` as shown in the following screenshot:
+
+![Screenshot from 2024-03-14 18-44-42](https://github.com/alanocallaghan/qupath-extension-template/assets/10779688/4712a209-eda7-4f80-8bed-bbab20e4f50a)
+
+This will automatically build the extension, and create a draft release containing the extension jar (and its associated sources and javadoc).
+You can then navigate to `Releases` and fill out information about the release --- the version, any significant changes, etc.
+Once published, users will be able to automatically install the extension as described here:
+https://qupath.readthedocs.io/en/0.5/docs/intro/extensions.html#installing-extensions
+
+### Automatic updates
+
+To enable easy installation and automatic updates in QuPath, fill in the (**public**) GitHub owner and repository 
+for the extension.
+
+https://github.com/qupath/qupath-extension-template/blob/778f02759d8a7fe5c73f1751edd58b6494beff9f/src/main/java/qupath/ext/template/DemoExtension.java#L65-L66
+
 ### Replace this readme
 
 Don't forget to replace the contents of this readme with your own!