fix: update README to include download badge and improve usage instructions

Author: c0rychu

README.md

@@ -1,6 +1,7 @@
 # physics-plot
 
 [![PyPI - Version](https://img.shields.io/pypi/v/physics-plot)](https://pypi.org/project/physics-plot/)
+[![PyPI - Downloads](https://img.shields.io/pypi/dm/physics-plot)](https://pypi.org/project/physics-plot/)
 
 `physics-plot` is a lightweight python package shipping a [Matplotlib style sheet](https://matplotlib.org/stable/gallery/style_sheets/style_sheets_reference.html) called [`pp_base.mplstyle`](https://github.com/c0rychu/physics-plot/blob/main/src/physics_plot/pp_base.mplstyle) and a few helper functions to create publication-quality plots with minimal effort.
 
@@ -20,10 +21,30 @@ pip install physics-plot
 
 ## Quick Start
 
+`physics-plot` can be installed via pip:
+```bash
+pip install physics-plot
+```
+
+There are basically two ways to use the `physics-plot` stylesheet. You can set it globally at the start of your script/notebook:
 ```python
 import matplotlib.pyplot as plt
 
 plt.style.use("physics_plot.pp_base")
+
+# ======================= #
+# Your plotting code here #
+# ======================= #
+```
+
+Or you can apply it to individual figures using a context manager:
+```python
+import matplotlib.pyplot as plt
+
+with plt.style.context("physics_plot.pp_base"):
+    # ======================= #
+    # Your plotting code here #
+    # ======================= #
 ```
 
 ## Examples