Improve installation instructions in the README

[Land0fChocolate]

The current installation instructions in the README are currently insufficient, especially with the addition of Python code in the project which the instructions give no guide to installing.

TODO:

1. Rewrite the installation guide in a clear and concise manner with its own instructions (not just pointing at how pokeemerald does it!), detailing the different steps; installing Ubuntu/WSL, installing devkitPro/GNU Arm Embedded Toolchain, installing agbcc, installing Python, installing Python dependencies, building make tools, running make, and anything else that could be needed.
   It will need to be ensured that other people can successfully replicate and run the project on their own systems with the instructions provided.

2. Build up a troubleshooting section.

[laqieer]

https://github.com/FireEmblemUniverse/fireemblem8u/blob/master/.github/workflows/build.yml

[Land0fChocolate]

Thanks, didn't notice those build instructions.

I'm having trouble with the Python aspect of the installation. My Ubuntu version uses Python3, so I use python3 -m pip install ttp numpy pillow, however it results in this message:

error: externally-managed-environment

× This environment is externally managed
╰─> To install Python packages system-wide, try apt install
    python3-xyz, where xyz is the package you are trying to
    install.

    If you wish to install a non-Debian-packaged Python package,
    create a virtual environment using python3 -m venv path/to/venv.
    Then use path/to/venv/bin/python and path/to/venv/bin/pip. Make
    sure you have python3-full installed.

    If you wish to install a non-Debian packaged Python application,
    it may be easiest to use pipx install xyz, which will manage a
    virtual environment for you. Make sure you have pipx installed.

    See /usr/share/doc/python3.12/README.venv for more information.

note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages.
hint: See PEP 668 for the detailed specification.

I used the virtual environment method to install the Python dependencies. pip show numpy shows that numpy is installed, but when I attempt to build the ROM with make I get the following:

/usr/bin/env: ‘python3\r’: No such file or directory
/usr/bin/env: use -[v]S to pass options in shebang lines
/usr/bin/env: ‘python3\r’: No such file or directory
/usr/bin/env: use -[v]S to pass options in shebang lines
scripts/gfxtools/tsa_generator.py graphics/efxdragon/DemonLightBg_Close_1.png graphics/efxdragon/DemonLightBg_Close_1.feimg1.bin graphics/efxdragon/DemonLightBg_Close_1.fetsa1.bin
Traceback (most recent call last):
  File "/mnt/c/Users/Tom/Saved Games/fireemblem8u/fireemblem8u/scripts/gfxtools/tsa_generator.py", line 4, in <module>
    import numpy as np
ModuleNotFoundError: No module named 'numpy'
make: *** [Makefile:179: graphics/efxdragon/DemonLightBg_Close_1.fetsa1.bin] Error 1