BREAKING CHANGE:
If you override compileSdkVersion<28  it won't work anymore.

The app was crashing with `"Could not find @ReactModule annotation in class RNCWebViewModule"` exception. Searching for this message in RN's code I found [this commit](0cd3994f1a/), introduced in React Native 0.58, which requires native modules to be annotated with @ReactModule annotation. 🤔 

After adding the annotation to the module, tapping on a file input field no longer crashes the app (in fact it shows the file browser). 🎉 

I haven't had caught it previously, testing only against React Native 0.57, sorry! 😞 

For reference see similar fix in `react-native-gesture-handler` — https://github.com/kmagiera/react-native-gesture-handler/pull/295.

Fixes https://github.com/react-native-community/react-native-webview/issues/458.

Added an extremely simple `.editorconfig` I inferred from the main part of the project, then reformatted the codebase according to it. 🙂

The current implementation doesn't support a list of file extensions in the accept attribute (e.g. `<input type="file" accept=".jpg, .png">`) while that is a valid value per the HTML spec. I've updated the implementation to convert any file extensions to mime types before we set the type(s) on the intent to rectify the issue. In addition I've updated the `acceptsImages` and `acceptsVideo` methods to handle file extensions as well.

Addresses #80.

Caveat: I am not an Android developer. This code comes from a fork of the original RN WebView that we have been using in production for some time, so all credit goes to @Oblongmana: https://github.com/Oblongmana/react-native-webview-file-upload-android.

Setting up a DownloadManager for the WebView is pretty straightforward, as is adding any known cookies to the request. Most of the complication comes from the requirement after SDK 23 to ask the user for the WRITE_EXTERNAL_STORAGE permission. Unfortunately there is no mechanism to suspend the download request until permission is resolved so this code stores off the request and sets up a listener that enqueues the download once permissions are resolved so the user experience is really nice.

I didn't see anything in the way of tests or documentation that needs to be added for this change, so let me know if I missed anything. Thanks!

Fixes #33 

I could really use some help from an Android developer on this one, because I just "made it work", don't know how to "make it work good".

Some things that should be reviewed:

- [ ] validate Android 5.0 devices (my emulator work, but outputs some weird sounds; a Galaxy 4 I tested on crashes)
- [ ] validate Android 5.1 devices (emulator works, couldn't find a real device)
- [ ] how to handle File Extensions? (https://www.w3schools.com/tags/att_input_accept.asp)

I'm sure that there's more refactoring to be done, so any help and advice would be appreciated.