Enable Emacs support for `rassumfrassum` LSP-multiplexer

[grayson-helmholz]

With the addition of ty, Emacs users would benefit from having the rassumfrassum LSP-multiplexer.

Before, just calling the built-in eglot-client (which chooses ruff by default in python buffers) in Emacs was sufficient to have a mostly equivalent workflow to VSCode users. This client does not support multiple LSP's like ruff and ty for the same major-mode (i.e python-mode).
Once installed, rassumfrassum can be called from Emacs with
C-u M-x eglot RET rass python RET
with 'rass python' being a shorthand to use ruff and ty.