allow more options to be configured in paru.conf and command line arguments

[getchoo]

This pull request allows for more internal configuration options (namely config.comments, config.makepkg_conf, and config.pager) to be changed in the configuration file and passed as command line arguments. I updated the shell completions and the defualt paru.conf to reflect the changes as well.

I only added cli arguments that I found to be a configuration option in src/config.rs but not in src/command_line.rs. I did something similar with the configuration file options by adding configuration options that were avalible but not present in the parse_*() functions of src/config.rs. I checked a few times to make sure I got them all, ignoring some options I believed shouldn't be included

...but I wouldn't be surprised if I missed some

[Morganamilo]

The goal of the provided config is to be an example and highlight some options that may be useful. Not everything is meant to be listed there.

Comments is a flag and doesn't really make sense as a config option.

makepkgconf is good to add though. It also appears to be missing from the man page.

Pager is probably fine though. It may be useful for if paru is called from some non shell script where you can't prefix env vars.

[getchoo]

I'll admit I definitley went overboard on the default config, but what options would you say should stay there? I was thinking of removing most of the *flags options, but keeping some like PreBuildCommand, MakepkgConf, Pager, Redownload, and NoCheck - since they would be likely used by at least some people (or at least by me with MakepkgConf for chroot builds).

I'll also add makepkgconf to the man page in a commit soon; i'm just a bit busy with finals

[Morganamilo]

The config should stay as is. There's a man page that lists all the options and people should read that.

[getchoo]

...I think I just accidentally pushed a horrible branch. Going to fix now

[getchoo]

Sorry about that, should be good now.

[getchoo]

fixed