This commit removes the common-lisp layer, as I do not use it anymore.
However, due to college, I need to be able to edit Swift code, hence its
addition.
This commit adds the `languagetool' layer to my Emacs configuration.
Since Emacs 27.1, fonts ligatures are supported with Cairo. The
`unicode-fonts' adds support for such feature using `ligatures.el'.
Due to the modification above, I changed my default font to Cascadia
Code.
