doc: add README

Author: chux0519

README.md

@@ -0,0 +1,17 @@
+# raspi demo for oled(ssd1306)
+
+in rust
+
+## Quick start
+
+> docker pull ragnaroek/rust-raspberry:1.39.0
+>
+> ./build.sh
+
+Then scp the release file to your raspi.
+
+## Example
+
+![picture](./images/01.jpg)
+
+![primitive](./images/02.jpg)