Support file sharing in the core Share plugin

[moberwasserlechner]

Sth like this:

Plugins.Share.shareFile({
      data: base64EncodedFileData,
      cacheDirectory?: "" // where to cache the file, which should be shared
})

[moberwasserlechner]

I develop this in a plugin first because it's easier to test across platforms.

See https://github.com/moberwasserlechner/capacitor-filesharer.

As soon as it is stable we could integrate it in the core if the need appears.

[jonathon-m]

Hopefully this will include support for Web Share API Level 2. Considering it's available in Chrome 75, it'll likely be standard soon.

[jcesarmobile]

Turns out Share plugin was already able to share files by using the url param, I've fixed it for Android too. So will close this issue once it's merged.

[jonathon-m]

Thanks @jcesarmobile !

[ionitron-bot]

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