Completes 406: stores the content of keybindings variable in a file for reuse.

[arkochan]

This pull requests holds upgrade to hypr/scripts/keybindings.sh as i mentioned before on https://github.com/mylinuxforwork/dotfiles/issues/406.

1. Rather than generating the keybinds variable from the keybind .conf (eg. hypr/keybindings/default.conf) file each time hypr/scripts/keybindings.sh script is ran, it is be generated once after each modification to keybind .conf file selected by user.

2. This variable is saved as [configfile.conf]_[unix_time_stamp].help file. the unix time stamp indicates the last time the config file is modified. if it dosent match the help file is regenerated according to the keybinds variable and older .help file is removed. The .help extension might not be the best choice. and i am a bit confused with the extension name. Also the help file is stored in the same directory as the conf direcotry. (eg .config/hypr/conf/keybindings by default)

This is my first PR in an open source project. Please do guide me if mistakes are made.