[FEAT] Set configuration file from ENV variable

[creizlein]

Description

It would be great if we can set the configuration file to be used via an environment variable.
FASTFETCH_CONFIG=/path/to/file.json

That way we don't need to specify it via command line and we can have different config files set per environment.

Motivation

Motivation comes due the fact that i have several different config files, one per Linux distribution, on a shared drive, with different names.

Right now, the only way to use a specific file per distribution is to pass it with command line arguments, but that is cumbersome when it would be specified via an environment variable.

Additional context

No response

[CarterLi]

fastfetch -c $FASTFETCH_CONFIG

Or, if you still want to use fastfetch in command line

# In .bashrc or similar
fastfetch() {
    if [ -n "$FASTFETCH_CONFIG" ]; then
        command fastfetch -c "$FASTFETCH_CONFIG" "$@"
    else
        command fastfetch "$@"
    fi
}