XDG Base Directory Specification

WIP, will flesh this out later:

What?

We should consider abiding by the XDG Base Directory Specification

This makes where notion lives on disk configurable, specifically it would abide by the following ENV variables:

$XDG_DATA_HOME fallback: $HOME/.local/share
$XDG_CONFIG_HOME fallback: $HOME/.config
$XDG_DATA_DIRS fallback: /usr/local/share/:/usr/share/
$XDG_CONFIG_DIRS fallback: /etc/xdg
$XDG_CACHE_HOME fallback: $HOME/.cache
$XDG_RUNTIME_DIR fallback see [spec]((https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html)
more details for each are specified here*

cluttering up $HOME becomes unwieldy
simplifies testing (we can sub-shell and simply set up the appropriate $XDG vars (no chroot, containers etc)
easier to reset config / clear caches
power users can configure to there hearts content, but no cost those who wish to rely on the fallbacks

Technically, likely via the XDG crate

Mostly just a list of whats in my $XDG_CONFIG_HOME, I suspect there are more.

Where do we put stuff in windows?

Maybe something like:

C:\Users\<username>\AppData\Local\notion-cli\notion\{dirs...}