Referrals: Entry point

[SergioEstevao]

| 📘 Part of: #2083 |
|:---:|

Fixes #
This PR adds the following:

• Adds a feature flag to control the display of referrals feature
• Implements the entry point on the Profile View Controller and show the pass badge

Note: The color of the badge is being worked on by design to correctly work on all themes

1	2	3	4	5

To test

• Start the app
• Ensure that have the Referrals FF active
• Go to Profile Tab
• If you are not logged in or don't have a subscription (Plus or Patron) you shouldn't see the gift icon on the top right
• Only if you are logged in and have a active Subscription you should see the gift icon
• Tap on the gift icon
• Check that the badge number overlayed on the gift icon goes down
• Check that when the number goes down to zero the badge icon is hidden

Checklist

• I have considered if this change warrants user-facing release notes and have added them to CHANGELOG.md if necessary.
• I have considered adding unit tests for my changes.
• I have updated (or requested that someone edit) the spreadsheet to reflect any new or changed analytics.