Add a `meta.member.access.python` scope wrapping around any attribute
access or method call.

Fixes MagicStack#188.

The `update-test` make target will automatically update the output of
any test that failed. This kind of bulk update is intended to be used
when the changes to scopes affect a large number of files. Of course, the
actual updated tests should still be reviewed for correctness.

Add `meta.attribute.python` to mark otherwise non-special attributes.
Add `meta.indexed-name.python` to mark the name of the object being
indexed.

In combination with `meta.member.access.python` the above scopes can
help highlight member access that is no otherwise using a builtin or
some other special case. For highlighting method names in method calls
the combination of `meta.member.access.python` and
`meta.function-call.generic.python` could be used.

Fixes MagicStack#188.

Correctly identify calls of the form "foo[123](bar=2)" to highlight the
contents of the parentheses as call arguments.

Issue: MagicStack#197

The "in" keyword is scoped as either `keyword.operator.logical.python`
or as `keyword.control.flow.python` depending on whether it appears as
part of a "for ... in" construct.

Fixes: MagicStack#193

MagicPython is still used by Linguist, but the actual syntax
hightlighting seems to be driven by something else now.  Thus, remove
the outdated statement from the README.

Closes: MagicStack#225

Add walrus operator `:=`.
Add positional only args separator `/`.
Add `=` to f-string formatting.

Fixes MagicStack#189

Any f-string allows variable interpolation, that includes a raw
f-string. Make all raw prefixes (`r` or `R`) behave the same way in
combination with `f` prefix.

Fixes MagicStack#186

Update the built-ins, dunders and add `match` and `case` keywords.