feat: add link previews to message composer

[isekovanic]

🎯 Goal

This PR adds the missing link previews feature that we've been missing on the React Native SDK.

It's essentially a way to prepopulate the message composer with a preview of the first link within the message we are composing, which is then going to be admitted as an attachment to the message we send.

As this is an optional feature, it first needs to be enabled by doing:

composer.updateConfig({
        linkPreviews: {
          enabled: true,
        }
      });

when configuring the composer state.

🛠 Implementation details

🎨 UI Changes

iOS

Before	After

Android

Before	After

🧪 Testing

☑️ Checklist

• I have signed the Stream CLA (required)
• PR targets the develop branch
• Documentation is updated
• New code is tested in main example apps, including all possible scenarios
  • SampleApp iOS and Android
  • Expo iOS and Android

[Stream-SDK-Bot]

SDK Size

title	develop	branch	diff	status
js_bundle_size	355 KB	355 KB	0 B	🟢