Allow wider Flow use

We (i.e. the jitsi-meet project) are using the haste module system on
Web as well, not only on React Native. Unfortunately, Flow does not
support .web.js by default. Override Flow's defaults to include .web.js
as well. Technically, we have .native.js as well so the choice of
.web.js may lead to errors. Practically though, it is a potential future
problem that we do not have at the time of this writing.

https://github.com/jitsi/jitsi-meet/pull/1397 will take advantage of the
wider Flow use. The PR in question is huge at the time of this writing.
In order to reduce it, I'm extracting changes not directly related to
React-ifying the Toolbar.

.flowconfig

@@ -49,5 +49,17 @@ suppress_comment=\\(.\\|\n\\)*\\$FlowFixedInNextDeploy
 
 unsafe.enable_getters_and_setters=true
 
+; We (i.e. the jitsi-meet project) are using the haste module system on Web as
+; well, not only on React Native. Unfortunately, Flow does not support .web.js
+; by default. Override Flow's defaults to include .web.js as well. Technically,
+; we have .native.js as well so the choice of .web.js may lead to errors.
+; Practically though, it is a potential future problem that we do not have at
+; the time of this writing.
+module.file_ext=.web.js
+; Flow's defaults:
+module.file_ext=.js
+module.file_ext=.jsx
+module.file_ext=.json
+
 [version]
 ^0.38.0