Expose search issue #3475

[jiahengguo123]

What is it?

• [ ] Bugfix (user facing)
• [x] Feature (user facing)
• [ ] Codebase improvement (dev facing)
• [ ] Meta improvement to the project (dev facing)

Description of the changes in your PR

• Exposed a search API via a custom URL scheme: Implemented the ability for third-party apps to initiate a search in NewPipe using a custom URL scheme newpipe://search?q=YOUR_QUERY.
• Added intent-filter to RouterActivity: Updated AndroidManifest.xml to include an intent-filter in RouterActivity to handle the custom URL scheme.
• Modified RouterActivity to handle the new intent: Updated RouterActivity to parse incoming intents with the newpipe://search scheme, extract the search query parameter, and start MainActivity with the necessary extras.
• Tested the implementation: Used ADB commands to send an intent with the custom URI and verified that NewPipe performs the search as expected.

Fixes the following issue(s)

• Fixes #3475

APK testing

The APK can be found by going to the "Checks" tab below the title. On the left pane, click on "CI", scroll down to "artifacts" and click "app" to download the zip file which contains the debug APK of this PR. You can find more info and a video demonstration on this wiki page.

Due diligence

• [x] I read the contribution guidelines.