CI: labeler.yml: add documentation label (#13506)

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/.github/labeler.yml b/.github/labeler.yml
index 6eef8d2..8764d96 100644
--- a/.github/labeler.yml
+++ b/.github/labeler.yml
@@ -8,6 +8,9 @@
 - any: ['.appveyor.yml']
 - any: ['.codecov.yml']
 
+documentation:
+- any: ['*/doc/*']
+
 translation:
 - any: ['src/po/*.po']