build: support pkg managers installation (#87)

closes #71, #84, #86
- AUR
- Homebrew
- Nix
- Debian (.deb)
- RPM (.rpm)
- Aqua
- ASDF

This is my first time doing this, so there might be mistakes. If you
can't download it through any pkg manager, please leave a comment or
open an issue

---------

Co-authored-by: use-the-fork <23747916+use-the-fork@users.noreply.github.com>

.envrc

@@ -0,0 +1,9 @@
+# Watch flake.nix for changes.
+watch_file flake.nix
+
+# Disable builders for trivial flake actions, such as direnv reload.
+# Helps us reduce overhead introduced by a redundant network request.
+if ! NIX_CONFIG="builders =" use flake . ; then
+  echo "Default shell could not be loaded." >&2
+  return 1
+fi