Add 1.1 feature support matrix

[paddybyers]

No description provided.

[mattheworiordan]

@paddybyers I added @Srushtika and @SimonWoolf to this PR for review.

I think we can do better than this for a few reasons:

• Why is Feature support the most important thing shown to a new developer who uses this client library. That is not the most important thing they need to know about, both because someone new to a library probably wants to know how to use it & install it first, but also because why are we focussing on the negative (of what's missing) first.
• There is no need to show users what features are supported, only what is not supported. A user is not arriving knowing anything about our release schedules in most cases. All they care about is the things I mentioned above, and any caveats. This section should be a caveat. I do think we should consider a separate table we maintain in one place which keeps a list of all unsupported features across all libraries in one place, but we can do that once the missing feature bit is done for all libs.
• You state "The 1.1 specification includes multiple new features, and this library implements a subset of those features as follows.". As above, the reader doesn't know about 1.0 or 0.8. So this is not needed.
• You state "The 1.1 specification also contains numerous spec clarifications, corrections and minor feature additions.". The reader does not care. Who is this README for?

[mattheworiordan]

@paddybyers ^?

[paddybyers]

@mattheworiordan updated: 0017497

[mattheworiordan]

This is brilliant, thanks @paddybyers.