Add README for Python package management

Added instructions for managing Python packages and using virtual environments.

scriptdata/uv/README.md

@@ -0,0 +1,49 @@
+## How to add/remove python package?
+
+1. Edit `requirements.in`. You may refer to [PyPI](https://pypi.org/) for possible package names.
+   - See also [uv doc](https://docs.astral.sh/uv/pip/dependencies/#using-requirementsin).
+2. Run `uv pip compile requirements.in -o requirements.txt` in this folder.
+
+## How will the python packages get installed?
+
+- They will be installed to the virtual environment `$ILLOGICAL_IMPULSE_VIRTUAL_ENV`.
+- The default value of `$ILLOGICAL_IMPULSE_VIRTUAL_ENV` is `$XDG_STATE_HOME/quickshell/.venv`.
+- See the function `install-python-packages()` defined in `/scriptdata/lib/package-installers.sh` for details.
+
+## How to use the python packages installed through here?
+
+Basically you'll need to activate the virtual environment first:
+```bash
+source $(eval echo $ILLOGICAL_IMPULSE_VIRTUAL_ENV)/bin/activate
+```
+then use the python package inside it;
+After that you probably need to deactivate it:
+```bash
+deactivate
+```
+### Situation 1: Call the command directly
+Take `kde-material-you-colors` as example.
+```bash
+source "$(eval echo $ILLOGICAL_IMPULSE_VIRTUAL_ENV)/bin/activate"
+kde-material-you-colors "$mode_flag" --color "$color" -sv "$sv_num"
+deactivate
+```
+
+### Situation 2: Use python script (wrapped)
+Take `generate_colors_material.py` as example:
+```bash
+source "$(eval echo $ILLOGICAL_IMPULSE_VIRTUAL_ENV)/bin/activate"
+python3 "$SCRIPT_DIR/generate_colors_material.py" "${generate_colors_material_args[@]}" \
+  > "$STATE_DIR"/user/generated/material_colors.scss
+"$SCRIPT_DIR"/applycolor.sh
+```
+
+### Situation 3: Use python script (shebang)
+**Note**: This method is only for simple situation.
+It can not deal with complex arguments (e.g. filaname containing spaces) passed to the python script.
+
+Take `generate_colors_material.py` as example, add the shebang below to its beginning:
+```python
+#!/usr/bin/env -S\_/bin/sh\_-c\_"source\_\$(eval\_echo\_\$ILLOGICAL_IMPULSE_VIRTUAL_ENV)/bin/activate&&exec\_python\_-E\_"\$0"\_"\$@""
+```
+Then you should run the script directly, i.e. `./generate_colors_material.py`, **not** `python3 generate_colors_material.py`.