build: allow to specify tag for workflow_dispatch

workflow_dispatch accepts also input values, so it's possible to trigger
a historical build. This is for example necessary to re-upload a Python
release which failed for some reason.

Signed-off-by: Daniel Wagner <[email protected]>

Author: igaw

.github/workflows/release-python.yml

@@ -7,6 +7,10 @@ on:
     tags:
       - '**'
   workflow_dispatch:
+    inputs:
+      tag:
+        description: 'Tag to check out'
+        required: false
 
 jobs:
   build_sdist: