Better help page

[TornaxO7]

Closes #78

Based on #91

[TornaxO7]

Generated output of cargo run -- --help:

A TUI for crates.io

Usage: crates-tui [OPTIONS]

Options:
      --print-default-config
          Print default configuration

  -c, --config-file <FILE>
          A path to a crates-tui configuration file
          
          [default: /home/tornax/projects/crates-tui/.config/config.toml]

      --color-file <FILE>
          A path to a base16 color file
          
          [default: /home/tornax/projects/crates-tui/.config/color.yaml]

  -f, --frame-rate <FLOAT>
          Frame rate, i.e. number of frames per second
          
          [default: 15]

      --data-dir <DIR>
          The directory to use for storing application data
          
          [default: /home/tornax/projects/crates-tui/.data]

      --log-level <LEVEL>
          The log level to use. Valid values are: error, warn, info, debug, trace, off.
          
          [default: info]

  -h, --help
          Print help (see a summary with '-h')

  -V, --version
          Print version

[joshka]

Rebased, removed the nix changes, added a splash of color: