Modify configs instead of overwriting

[MFelida]

Bundle yq in the tarball and assign values instead of overwriting the whole file.

[CheapFuck]

Hi! I started on this and hit a format-compatibility wall with yq that I think changes the approach, so sharing findings + a proposal before opening a PR.

The three files the installer writes are three different formats, and mikefarah/yq can't safely round-trip any of them:

File	Format	yq support
user/config/containers/storage.conf	TOML	read-only — yq has no TOML encoder (output is only yaml/json/props/csv/tsv/xml), so it can't write the file back out as TOML
user/config/distrobox/towel.ini	INI ([towel] section)	unsupported — yq has no INI decoder or encoder
user/config/distrobox/distrobox.conf	shell-sourced key="value"	closest is -p=props -o=props, but props output is key = value (space-separated, values unquoted) which breaks distrobox, since it sources this file as shell

So yq alone can't cover storage.conf (TOML) or towel.ini (INI), and props mode would corrupt distrobox.conf's shell syntax. (Refs: yq convert / properties docs — no TOML/INI pages exist.)

Proposal — get the same benefit (preserve the user's edits, only set the keys towel actually owns) without shipping a ~10 MB binary or a TOML/INI library:

A small, dependency-free bash helper that sets one key=value (optionally within an INI/TOML [section]) in place — creating the file/section/key if missing, leaving everything else untouched. The installer calls it once per managed key, e.g.:

config_set_section "$USER_CONFIG/distrobox/towel.ini"          towel   image  "quay.io/fedora/fedora-toolbox:rawhide"
config_set_section "$USER_CONFIG/containers/storage.conf"      storage driver '"overlay"'
config_set_kv      "$USER_CONFIG/distrobox/distrobox.conf"     container_manager '"podman"'

This:

• preserves any other keys/comments the user added,
• is idempotent (re-running ./install is a no-op when values already match),
• needs no bundled binary, pin, or checksum (unlike the distrobox download path).

If you'd still prefer to bundle a tool, one that does handle TOML+INI would be required (e.g. dasel for TOML, crudini for INI) — but that's two extra tools with the same pin/checksum/multi-arch maintenance as the distrobox download.

Happy to implement the native-helper version — want me to go ahead with that, or do you have a preference on the tooling?