Feature: RSR staking yield estimator

[SharkofMirkwood]

Hello, I have been following Reserve for a while and this is a draft of a contribution I'd like to offer to the Register app. This PR adds a new page with a staking yield estimator, as outlined by 0xJMG on the forum: https://forum.reserve.org/t/rtoken-staking-estimator-worksheet/1009

The logic used is the same as the spreadsheet, but it looks at all the featured RTokens and makes the yield calculations for these tokens, pointing to the staking page for each one.

There are a couple of improvements I'd like to make, either as part of this PR or later on if you prefer to ship incrementally. For example:

• Allowing end users to tweak the parameters used in the calculations (e.g. calculate yield for values other than 100k RSR staked; modify the existing RSR staked to see the impact on yield per RSR token...)
• An introduction or some explaination of what the user is looking at
• Show the yield estimates in RSR as well as USD

However, I think there is value in this page as it is and so I'm opening this PR as a draft while I work on these improvements.
I noticed you have feature branches being deployed from GitHub Actions (though not sure if that's only for team members' contributions!), so my aim is to share the work in progress to the forum for evaluation as well as get some early-ish feedback on the PR itself. For a start I'm not even certain whether this contribution to the app is desired.

Here is a screenshot of the new page:

[lcamargof]

love it!