Welcome rewards flow

[L03TJ3]

Description

For a select group of users we want to show a welcome offer when they sign up for wallet-v2. This PR includes:

• [x] The WelcomeOfferModal
• [x] Show Modal based on (TBD) <-- decided on location/web-app use
• [x] Track in amplitude (invited/seen)

UI

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

Checklist:

• [ ] PR title matches follow: (Feature|Bug|Chore) Task Name
• [ ] My code follows the style guidelines of this project
• [ ] I have followed all the instructions described in the initial task (check Definitions of Done)
• [ ] I have performed a self-review of my own code
• [ ] My changes generate no new warnings
• [ ] I have added tests that prove my fix is effective or that my feature works
• [ ] New and existing unit tests pass locally with my changes
• [ ] I have added reference to a related issue in the repository
• [ ] I have added a detailed description of the changes proposed in the pull request. I am as descriptive as possible, assisting reviewers as much as possible.
• [ ] I have added screenshots related to my pull request (for frontend tasks)
• [ ] I have pasted a gif showing the feature.
• [ ] @mentions of the person or team responsible for reviewing proposed changes