add step to verify docs on area/documentation PRs (#1528)

* add step to verify docs on area/documentation PRs

* use GH actions to run the verification

* add check if label is set to area/documentation

* fix broken links in docs with WIP files

* add generating API docs before verifying

Signed-off-by: Sebastian Malton <sebastian@malton.name>

docs/extensions/guides/anatomy.md

@@ -0,0 +1,3 @@
+---
+WIP
+---

docs/extensions/guides/components.md

@@ -0,0 +1,3 @@
+---
+WIP
+---

docs/extensions/guides/kube-object-list-layout.md

@@ -0,0 +1,3 @@
+---
+WIP
+---

docs/extensions/guides/stores.md

@@ -0,0 +1,3 @@
+---
+WIP
+---