Switch to npm, make packaging easier for linux users

[getchoo]

These changes are targeted towards helping out our Linux users in both using and packaging this app. This is work towards #497 - with it hopefully being the most we need to do here to the app itself - supersedes part of #559, and will help #561. Downstream PRs like flathub/flathub#4950 and NixOS/nixpkgs#289149 will also be able to take advantage of this on the next release.

The most impactful change for all platforms here will be the switch to npm. Though pnpm arguably has a better UX, it isn't supported well by most packaging systems (like nixpkgs), and in some cases not at all (flatpak); in contrast, npm is more well known and basically universally supported. Another change (exclusive to Linux) is that now all builds will be based on the latest Ubuntu LTS. This was done for two reasons:

• There isn't much reason to build again 20.04
• I believe artifacts from there were being uploaded instead. This means binaries distributed by Modrinth will be built again openssl v3. This should fix libssl.so.1.1 is not a dependancy in the deb #239, Error upon launching on Ubuntu #867, .deb doesent work in kde neon #991, deb: missing shared library under Pop!-OS #1065

Lastly, git dependencies have been dropped in our Node deps as they can also introduce difficulties packaging, and the .desktop file included in the deb package has much more detailed metainfo

[getchoo]

@Geometrically