Add term entry for matplotlib.pyplot.step with example image (#7984)

* Add term entry for matplotlib.pyplot.step with example image

* minor content fixes

* Update step.md

* format fixes

---------

Author: GregoryCardillo

content/matplotlib/concepts/pyplot/terms/step/step.md

@@ -0,0 +1,73 @@
+---
+Title: 'step()'
+Description: 'Draws step plots where y-values change at discrete x-positions.'
+Subjects:
+  - 'Data Science'
+  - 'Data Visualization'
+Tags:
+  - 'Graphs'
+  - 'Libraries'
+  - 'Matplotlib'
+  - 'Methods'
+CatalogContent:
+  - 'learn-python-3'
+  - 'paths/data-science'
+---
+
+**`step()`** creates a piecewise-constant (step) plot from 1-D data. Each sample in `y` is represented as a horizontal segment and adjacent samples are connected by vertical lines. The `where` parameter controls whether the step change happens before, after, or at the midpoint of the x-coordinate.
+
+## Syntax
+
+```pseudo
+matplotlib.pyplot.step(x, y, *args, where='pre', **kwargs)
+```
+
+**Parameters:**
+
+- `x` (array-like): 1-D sequence of x positions. It is assumed (but not enforced) that `x` is increasing.
+- `y` (array-like): Sequence of y-values. Must have the same length as `x`.
+- `*args`: positional arguments forwarded to `plot()` (for example a format string such as `'o-'`).
+- `where` ({ `'pre'`, `'post'`, `'mid'` }, optional) — controls the placement of the steps:
+  - `'pre'` (default): the y value is constant to the left of each x position; the interval `(x[i-1], x[i]]` has value `y[i]`.
+  - `'post'`: the y value is constant to the right of each x position; the interval `[x[i], x[i+1])` has value `y[i]`.
+  - `'mid'`: each step is centered between neighbors; level changes occur at midpoints between successive x values.
+- `**kwargs`: any other keyword arguments accepted by `matplotlib.pyplot.plot`, such as `label`, `linewidth`, `linestyle`, `alpha`, etc.
+
+**Returns:**
+
+A list of `matplotlib.lines.Line2D` objects representing the plotted steps.
+
+> **Notes:**
+>
+> - Use `plt.stairs()` if you have explicit step edges (left/right boundaries) rather than sample positions.
+> - `step()` is a thin wrapper around `plot()` and supports most `plot` formatting options.
+
+## Example
+
+The example below draws three three-step series using `where='pre'`, `where='mid'`, and `where='post'`.
+
+```py
+import numpy as np
+import matplotlib.pyplot as plt
+
+x = np.linspace(0, 5, 6)
+y = np.array([0, 1, 0, 1, 0, 1])
+
+plt.figure(figsize=(6, 3))
+plt.step(x, y + 2, where='pre', label="pre")
+plt.step(x, y + 1, where='mid', label="mid")
+plt.step(x, y + 0, where='post', label="post")
+
+plt.ylim(-0.5, 3.5)
+plt.xlabel('x')
+plt.ylabel('y')
+plt.title('Example: matplotlib.pyplot.step')
+plt.legend()
+plt.grid(True)
+
+plt.show()
+```
+
+The output of this code will be:
+
+![Step plot example](https://raw.githubusercontent.com/Codecademy/docs/main/media/pyplot-step-example.png)