config.json -> config.toml

[aw-bib]

Only documentary.

The welcome screen of the docs still refers to config.json while the docs only talk about toml.

BTW: if it is easy it may be convenient for the welcome screen to actually expand $CONFIG_DIR. I got a bit confused as the profiles seem to be moved to .local/share/iamb while there is an older profiles in .config/iamb as well. So at first I was unsure where to put it, as $CONFIG_DIR is no variable on Linux.

isRelatedTo: #229

[ulyssa]

Expanding $CONFIG_DIR is a little difficult due to how welcome.md is currently read in, but I have thought about overhauling the Welcome window at some point to make it more interactive than a read-only text window. When I do that, I can take a look at showing the actualy location. For now, I've just put ~/.config/iamb/config.toml in there as an example for XDG environments.