Upgrade xtext to 2.28 and eclipse to 2022-09 and drop Java 8 #568

	# To verify that changes of a PR do not break elkjs.
	name: elkjs

	on:
	pull_request:
	branches:
	- master

	jobs:
	build:
	runs-on: ubuntu-latest
	strategy:
	matrix:
	# We check against LTSs supported by GWT
	# 8 - LTS
	# 11 - LTS
	java-version: [ 11 ]
	node-version: [ 12.x ]

	steps:
	# Checkout the repository of both elk and elkjs, place them next to each other.
	- uses: actions/checkout@v2
	with:
	path: elk
	- uses: actions/checkout@v2
	with:
	repository: kieler/elkjs
	path: elkjs
	# Prepare and use caches for both gradle and npm.
	- name: Cache gradle packages
	uses: actions/cache@v1
	with:
	path: ~/.gradle/caches
	key: ${{ runner.os }}-gradle-${{ hashFiles('*/.gradle') }}
	restore-keys: ${{ runner.os }}-gradle
	- name: Cache npm
	uses: actions/cache@v1
	with:
	path: ~/.npm
	key: ${{ runner.os }}-node-${{ hashFiles('**/package.json') }}
	restore-keys: ${{ runner.os }}-node-
	# elkjs (or rather GWT) requires Java 1.8
	- name: Set up JDK ${{ matrix.java-version }}
	uses: actions/setup-java@v1
	with:
	java-version: ${{ matrix.java-version }}
	- name: Grant execute permission for gradlew
	run: chmod +x $GITHUB_WORKSPACE/elkjs/gradlew
	- name: Use Node.js ${{ matrix.node-version }}
	uses: actions/setup-node@v1
	with:
	node-version: ${{ matrix.node-version }}
	# Finally build elkjs and run its tests
	- name: npm install, build, and test
	run: \|
	npm install
	npm run build --if-present
	npm test
	working-directory: /home/runner/work/elk/elk/elkjs/
	env:
	CI: true

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