feat(ramp): add sell deeplink

[wachunei]

Description

This PR adds the handling for the Sell flow deeplink, the same way we did for Buy flow in #5743:

This PR adds support for metamask://sell-crypto and https://metamask.app.link/sell-crypto, these will open the sell flow.

Related issues

Fixes:

Manual testing steps

1. Navigate to metamask://sell-crypto or https://metamask.app.link/sell-crypto
2. Sell flow must open

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I’ve followed MetaMask Coding Standards.
• I've clearly explained what problem this PR is solving and how it is solved.
• I've linked related issues
• I've included manual testing steps
• I've included screenshots/recordings if applicable
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.
• I’ve properly set the pull request status:
  • In case it's not yet "ready for review", I've set it to "draft".
  • In case it's "ready for review", I've changed it from "draft" to "non-draft".

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

100.0% Coverage
0.0% Duplication

[bkirb]

@wachunei LGTM I verified both deeplinks ✅

[sethkfman]

LGTM