Test some GitHub Actions (PHPStan)

.gitattributes

@@ -1,3 +1,4 @@
+/.github export-ignore
 /features export-ignore
 /tests export-ignore
 

.github/main.workflow

@@ -0,0 +1,10 @@
+workflow "Main Workflow" {
+  on = "push"
+  resolves = ["PHPStan"]
+}
+
+action "PHPStan" {
+  uses = "docker://oskarstark/phpstan-ga"
+  secrets = ["GITHUB_TOKEN"]
+  args = "analyse --level=max src/"
+}