ci: skip old tags (#33)

* chore: skip if docs yml doesn’t exist

* chore: skip tags

---------

Co-authored-by: danthorpe <danthorpe@users.noreply.github.com>

Author: danthorpe

.github/workflows/docs.yml

@@ -50,9 +50,10 @@ jobs:
 
               git checkout .;
               git checkout "$tag";
-
-              make docs-all tag="$tag" output=docs-out basepath=swift-utilities
-
+              if [ -f ".github/workflows/docs.yml" ]
+              then
+                make docs-all tag="$tag" output=docs-out basepath=swift-utilities
+              fi;
             fi;
           done