Reduce binary size

Currently, as of harper 0.64.0, the harper-ls-aarch64-unknown-linux-gnu binary on my machine weights 48M, which is a tad enormous for a command-line utility processing text. It's more than:
- a (minimal) [Linux distribution (alpine-virt)](https://www.alpinelinux.org/downloads/)
- the typst binary, which is doing parsing, processing, complex rendering pdf generation, … and their binary even embeds fonts!
- two times the size of the emacs binary

I know that "disk is cheap", but not everyone is using brand new hardware with terabytes of space, and even if it were the case, due to the rapid release schedule of harper, it ends up taking a significant amount of space on Linux distribution packages mirrors/archives.

The fact that the [release page](https://github.com/Automattic/harper/releases/tag/v0.64.0) shows that the .tar.gz archive weights only ~7M hints that the dictionaries aren't compressed, which would be a quick win.

Start by inspecting the harper-ls release build and the dictionary assets, then compare the binary with the .tar.gz contents described in the issue. Determine whether dictionary compression reduces the shipped binary size; done means a materially smaller release binary without changing grammar-checking behavior.

Written by the indexing model from the issue text.