c-lightning-REST: OpenChannel: make feerate options clear

[kaloudis]

Description

Relates to issue: ZEUS-460

Fee options when opening channel for c-lightning-REST are urgent, normal, and slow. We must make this clear to the user. Future iterations will use a GUI component, such as radio buttons.

https://github.com/Ride-The-Lightning/c-lightning-REST/blob/master/docs/channelmgmt.md

This pull request is categorized as a:

• New feature
• Bug fix
• Code refactor
• Configuration change
• Locales update
• Other

Checklist

• I’ve run npm run tsc and make sure my code didn’t produce errors
• I’ve run npm run prettier and formatted my code correctly

Testing

If you added new functionality or fixed a bug, did you add new unit tests?

• No, I’m a fool
• Yes
• N/A

I have tested this PR on the following platforms (please specify OS version and phone model/VM):

• Android
• iOS

I have tested this PR with the following types of nodes (please specify node version and API version where appropriate):

• LND
• c-lightning-REST
• spark
• Eclair
• LndHub

Locales

• I’ve added new locale text that requires translations
• I’m aware that new translations should be made on the Zeus Transfix page and not directly to this repo

Third Party Dependencies and Packages

• Contributors will need to run npm install after this PR is merged in
• 3rd party dependencies have been modified:
  • verify that package.json and package-lock.json have been properly updated
  • verify that dependencies are installed for both iOS and Android platforms

Other:

• Changes were made that require an update to the README
• Changes were made that require an update to onboarding