Fix POSIX Compatibility issue '[[' and Refactor Font installations step.

[RazoBeckett]

1. Update Font Installation Process:

• Updated the font URL for FiraCode from version 2.3.3 to 3.2.1.
• Added a check to verify the accessibility of the font URL before attempting to download.
• Improved the installation process by using a temporary directory to handle downloaded files.

2. Replaced [[ ... ]] with [ ... ] in the conditional statement for dnf package manager detection.

[manishjchoudhary]

a77df1e can fix issue #77.
But as I saw in another issue where someone mentioned not seeing the icons correctly #65, people still have to go and change either the terminal / global font so, why install a random Nerd font at all?
Why not do as I mentioned here. Thoughts?

[RazoBeckett]

Hey @manishjchoudhary , the thing is, this process is meant to be automated. Asking the user to visit a website and manually install the font requires effort. Users need to set the font manually for their terminal since everyone has their own preferences. You might prefer using Kitty, while I might be on Alacritty.