Document Python syntax support

[lieryan]

Need to go through Python's Change Log and identify syntax changes.

We should start documenting the syntax support in rope as it currently.

Create a table containing a list of these syntaxes, divided by Python version, and a checklist of how well they are currently supported in rope.

Three main area of focus are:

• renaming of variables around that new syntax
• extract local variables for expressions containing that syntax
• extract method refactoring of block of codes that contains that syntax, including whether variable scopes are detected correctly

Subtickets:

• [ ] #383
• [ ] break this ticket into major Python versions from 3.0 to 3.9