Use Web Share API

[raucao]

Instead of just showing the URL we can (soon) add a button that invokes the native sharing options on e.g. Android devices:

https://developers.google.com/web/updates/2016/10/navigator-share

This can already be tested by registering an origin for Chrome's beta test of this feature. The spec isn't final yet; development is happening here: https://github.com/WICG/web-share

[raucao]

Looks like it's already enabled by default in current Chrome for Android stable: https://www.chromestatus.com/features/5668769141620736

[raucao]

Even better, we can make Sharesome a target for sharing images. Mastodon just implemented that e.g.:

• Demo: https://mstdn.maud.io/@rinsuki/99363572785336264
• PR: implement web share target mastodon/mastodon#6278

Edit: currently not possible, but being discussed in w3c/web-share#12

[raucao]

Update: sharing files is now possible using the Web Share Target API, Level 2. However, it's not implemented anywhere yet. Will probably launch in Chrome sometime this year.