Fix CODEGEN library rendering: add missing blank line before Controllers heading

Author: apetros

src/content/docs/developer/codegen-library.mdx

@@ -1022,6 +1022,9 @@ Unlike **inlim**, the bounds $x_{min}$ and $x_{max}$ are model states (variables
 The non-windup behaviour is identical to **inlim**: integration halts when a limit is reached and resumes once the input drives the output away from that limit.
 
 $T = 0$ is not allowed. If $T$ is too small, the solver may encounter a singularity and the simulation may fail.
+
+---
+
 ## Controllers
 
 ### `pictl`