Update blueprint.yml

.github/workflows/blueprint.yml

@@ -58,6 +58,7 @@ jobs:
             pip install pygraphviz --global-option=build_ext --global-option="-L/usr/lib/graphviz/" --global-option="-R/usr/lib/graphviz/"
             pip install leanblueprint
             leanblueprint pdf
+            mkdir docs
             cp blueprint/print/print.pdf docs/blueprint.pdf
             leanblueprint web
             cp -r blueprint/web docs/blueprint