improve entering release notes into fastlane

[CDRussell]

Task/Issue URL: https://app.asana.com/0/488551667048375/1200292136839127/f
Tech Design URL:
CC:

Description:

Steps to test this PR:
ℹ️ Open Fastfile, and comment out line 145 (so it becomes #ensure_git_branch( branch: 'develop' ))

Test keeping existing release notes

1. Run bundle exec fastlane release
2. Verify you see the existing release notes
3. Choose option 1 which is to "KEEP EXISTING" release notes
4. Enter any version number (e.g., 0)
5. Verify the release notes that are printed are the same as before
6. 🛑 enter n to end this flow

Test using custom release notes

1. Run bundle exec fastlane release
2. Choose option 2 which is to use "CUSTOM" release notes
3. Verify you are prompted to enter custom release notes. Enter some (test multi-line release notes) and terminate the notes by entering END and pressing enter
4. Enter any version number (e.g., 0)
5. Verify the custom release notes you entered are displayed
6. 🛑 enter n to end this flow

Test using standard release notes

1. Run bundle exec fastlane release
2. Choose option 3 which is to use standard bug fix release notes ("Bug fixes and other improvements")
3. Enter any version number (e.g., 0)
4. Verify the "Bug fixes and other improvements" release notes are displayed
5. 🛑 enter n to end this flow

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Internal references:

Software Engineering Expectations
Technical Design Template

[aitorvs]

This is gold! Thanks @CDRussell for championing this!

[joshliebe]

Nice upgrade, good job 👍