Ignore root docs folder in Flow config

Otherwise Flow finds obscure files in docs/vendor.
Seems like you'd only get them if you have a local checkout of docs Ruby dependencies.
This explains why Travis didn't fail.

.flowconfig

@@ -7,6 +7,7 @@
 <PROJECT_ROOT>/.*/__tests__/.*
 
 # Ignore Docs
+<PROJECT_ROOT>/docs/.*
 <PROJECT_ROOT>/.*/docs/.*
 
 [include]