Add Linux installation instructions

[mathsvisualization]

Added installation instructions for Linux (Ubuntu/Debian), including required system dependencies, optional lightweight LaTeX setup, and optional virtual environment (venv) instructions.

Motivation

The README currently contains installation instructions for Windows and MacOS, but lacks a dedicated Linux installation section. This change adds clearer setup instructions for Ubuntu/Debian-based distributions, making it easier for Linux users to get started with ManimGL.

It also documents a lightweight LaTeX installation alternative instead of requiring the much larger texlive-full package.

Proposed changes

• Added a dedicated Linux (Ubuntu/Debian) installation section
• Added installation steps for required system dependencies (ffmpeg, python3-pip, libpango1.0-dev)
• Added optional lightweight LaTeX installation instructions
• Added optional virtual environment (venv) setup instructions

Lightweight LaTeX alternative

Instead of installing the much larger texlive-full package, the following lightweight setup was documented:

sudo apt install texlive-science texlive-fonts-extra texlive-latex-extra 

This setup was sufficient for rendering LaTeX in ManimGL during testing while requiring significantly less disk space compared to texlive-full.

Screenshot attached below showing the approximate package size/install size during setup.

Test

Code:

sudo apt update

sudo apt install ffmpeg
sudo apt install python3-pip
sudo apt install libpango1.0-dev

sudo apt install texlive-science texlive-fonts-extra texlive-latex-extra

git clone https://github.com/3b1b/manim.git
cd manim

python3 -m pip install -e .
manimgl example_scenes.py OpeningManimExample 

Result:

ManimGL installed successfully and example scenes rendered correctly on Ubuntu/Debian-based Linux systems.