docs: run GitHub action when Charts are touched to check Helm values ref

PR cilium#16238 added a reference for the Helm values in the Charts to the
documentation. A number of these values are not common words from the
dictionary, and need to be added to the list of acceptable words in the
spelling list as we update the charts.

The GitHub action for documentation is supposed to help with the task,
catching omitted keywords. But it is only run when a number of
documentation-related files are run, and this does not currently include
the Charts! Let's fix in order to catch spelling mistake (or omitted
spelling list updates).

Fixes: cilium#16238
Signed-off-by: Quentin Monnet <quentin@isovalent.com>

.github/workflows/documentation.yaml

@@ -35,6 +35,7 @@ jobs:
               - 'cilium-health/cmd/**'
               - 'daemon/cmd/**'
               - 'hubble-relay/cmd/**'
+              - 'install/kubernetes/**/'
               - 'operator/cmd/**'
 
   # Runs only if code under Documentation or */cmd/ is changed as the docs