Problems with install script: Using `apt`

[harshcurious]

Describe the bug Errors while installing this package on Manjaro/Arch linux

To Reproduce Steps to reproduce the behavior:

1. running bash GIMP-ML/install.bat results in a bunch of errors:
   • sudo: apt-get: command not found
   • sudo: apt: command not found : These two are because apt is not the package manager for Manjaro
   • python: can't open file 'GIMP-ML/get-pip.py': [Errno 2] No such file or directory [^get-pip]

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS Version: Manjaro
• GIMP Version: 2.99.8-1

[^get-pip]: Happens after I get:

    Resolving bootstrap.pypa.io (bootstrap.pypa.io)... 199.232.20.175, 2a04:4e42:42::175
    Connecting to bootstrap.pypa.io (bootstrap.pypa.io)|199.232.20.175|:443... connected.
    HTTP request sent, awaiting response... 200 OK
    Length: 2159352 (2.1M) [text/x-python]
    Saving to: ‘get-pip.py’

    get-pip.py                      100%[====================================================>]   2.06M  9.29MB/s    in 0.2s    

    2021-11-29 11:57:04 (9.29 MB/s) - ‘get-pip.py’ saved [2159352/2159352]

    python: can't open file 'GIMP-ML/get-pip.py': [Errno 2] No such file or directory

I don't think you need to download pip. It should be installed on most systems anyways or otherwise make it a system requirement.