Add key features to to the RPC providers grid

[johncanneto]

Today we just show whether they support horizon or RPC and which env they use. I want to add some more information about the key features they support (like Overcat's getLedgers proxy)

[ElliotFriend]

@sydneynotthecity any thoughts on if this is a relevant issue, still?

Edit: looks like it did get shipped in #1761 (Dedicated Nodes + RPC Archive columns with the getLedgers footnote) and the issue just never got closed. Closing as completed — shout if you have more feature columns in mind and we'll open a fresh scoped issue.