replace travis with github actions (#1452)

.github/workflows/linting.yaml

@@ -0,0 +1,28 @@
+name: Code Styles
+on:
+    pull_request: null
+    push:
+        branches:
+            - master
+jobs:
+    tests:
+        runs-on: ubuntu-latest
+        strategy:
+            matrix:
+                php: ['7.4']
+
+        name: PHP ${{ matrix.php }}
+        steps:
+            -   uses: actions/checkout@v2
+            -   uses: shivammathur/setup-php@v1
+                with:
+                    php-version: ${{ matrix.php }}
+                    coverage: none
+                    extensions: intl
+                    tools: cs2pr:1.0.1
+            -   run: composer install --no-progress
+            -   run: composer validate --no-check-all --strict
+            -   run: vendor/bin/php-cs-fixer fix --dry-run --verbose --config=.php_cs.dist --using-cache=no --show-progress=none --format=checkstyle | cs2pr
+            -   run: vendor/bin/phpstan analyse src -c phpstan.neon --level=3 --no-progress --error-format=checkstyle | cs2pr
+            -   run: vendor/bin/phpstan analyse tests -c tests/phpstan.neon --level=4 --no-progress --error-format=checkstyle | cs2pr
+            -   run: composer kimai:code-lint