[flow] ignore hidden directories (#28096)

[flow] ignore hidden directories

Author: kassens

scripts/flow/config/flowconfig

@@ -2,7 +2,8 @@
 .*/scripts/bench/.*
 .*/build/.*
 .*/fixtures/.*
-.*/.tempUserDataDir/.*
+# Any hidden directory
+.*/\..*
 
 # These shims are copied into external projects:
 .*/rollup/shims/facebook-www/.*