Added pointer to RP2040 docs

Author: edwardalee

docs/embedded/rp2040.mdx

@@ -0,0 +1,12 @@
+---
+title: RP2040
+description: Developing LF Programs for RP2040.
+---
+# Overview
+Lingua Franca's C-runtime supports the [Raspberry Pi RP2040](https://en.wikipedia.org/wiki/RP2040),
+an inexpensive microcontroller that is typically used without an operating system ("bare metal").
+A series of lab excercises have been developed for instructional use, but these also
+serve as the best documentation and guide for developing programs for the RP2040.
+These lab exercises use the [Pololu 3pi+ 2040 robot](https://www.pololu.com/docs/0J86),
+which has an RP2040, but the exercises can be adapted to other robots and RP2040 platforms.
+See the [RP2040 lab page](https://lf-lang.org/embedded-lab/) for more information.

docs/sidebars.ts

@@ -179,6 +179,10 @@ const sidebars: SidebarsConfig = {
         {
           "type": "doc",
           "id": "embedded/zephyr"
+        },
+        {
+          "type": "doc",
+          "id": "embedded/rp2040"
         }
       ]
     },