Generate and keep in the repo the missing image in the README

Fixes #2

README.md

@@ -29,7 +29,7 @@ fig.savefig("plot.pdf")?;
 ```
 
 
-![Basic Example](https://matplotlib.org/stable/_images/sphx_glr_quick_start_001_2_0x.png)
+![Basic Example](examples/basic_example.svg)
 
 
 [Matplotlib]: https://matplotlib.org/

examples/a_simple_example.rs

@@ -9,6 +9,6 @@ fn main() -> Result<(), Box<dyn Error>> {
     let y: Vec<_> = x.iter().map(|x| x.sin()).collect();
     ax.xy(&x, &y).fmt("r.").plot();
     // plt::show();
-    fig.save().to_file("examples/a_simple_example.svg")?;
+    fig.save().to_file("target/a_simple_example.svg")?;
     Ok(())
 }

examples/basic_example.rs

@@ -0,0 +1,10 @@
+// Example for the README
+
+use matplotlib as plt;
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let (fig, [[mut ax]]) = plt::subplots()?;
+    ax.xy(&[1., 2., 3., 4.], &[1., 4., 2., 3.]).plot();
+    fig.save().to_file("examples/basic_example.svg")?;
+    Ok(())
+}