Add 'Radio' lesson to csintro. (#435)

* Local commit.

* Add 'Radio' lesson to csintro.

docs/courses/csintro/radio.md

@@ -0,0 +1,31 @@
+# Radio and Communication
+
+This lesson covers the use of more than one micro:bit to share and combine data. Students will explore a complex epidemiological program (Infection) that demonstrates the Radio functionality of the micro:bit. Students will send and receive numbers and strings in a series of guided activities. Finally, students are asked to collaborate so that they can share their micro:bits and create a project together.
+
+![Radio wave diagram](/static/courses/csintro/radio/radio-wave.png)
+
+## Lesson objectives
+
+Students will...
+* Understand how to use the Radio blocks to send and receive data between micro:bits
+* Understand the specific types of data that can be sent over the Radio
+
+## Lesson structure
+
+* Introduction: Radio & Communication
+* Unplugged Activity: Infection Simulation
+* Micro:bit Activity: Marco Polo & Morse Code
+* Project: Radio
+* Assessment: Rubric 
+* Standards: Listed
+
+## Lesson plan
+
+1. [**Overview**: Radio and communications](/courses/csintro/radio/overview)
+2. [**Unplugged**: Infection simulation](/courses/csintro/radio/unplugged)
+3. [**Activity**: Marco Polo and Morse code](/courses/csintro/radio/activity)
+4. [**Project**: Radio project](/courses/csintro/radio/project)
+
+## Related standards
+
+[Targeted CSTA standards](/courses/csintro/radio/standards)