docs: Enhance fonttools installation instructions and error messages to differentiate between pip and pipx usage.

README.md

@@ -18,11 +18,18 @@ Ensure the following tools and libraries are installed and accessible in your sy
 2. **MKVToolNix** (specifically `mkvmerge` and `mkvextract`)
 3. **fonttools** (Python library)
 
-Install the required Python dependency via pip:
+Install the required Python dependency:
+
+For Windows or Ubuntu, you can use `pip`:
 ```bash
 pip install fonttools
 ```
 
+For ArchLinux (or if your system enforces PEP 668), it is recommended to use `pipx`:
+```bash
+pipx install fonttools
+```
+
 ## Usage
 Simply place the script inside the directory containing the `.mkv` files you wish to process and run it. You can also place the script in your personal `bin` or `PATH` folder to run it from anywhere.