Fix formatting errors in README.rst

The code blocks added by pine64#17 were formatted as Markdown, but this is an
reStructuredText file.

README.rst

@@ -1,5 +1,5 @@
 BLE602 SDK
-=========
+==========
 
 `Discord <https://discord.gg/89VWQVH>`_ , `Telegram <https://t.me/joinchat/Kmi2S0nOsT240emHk-aO6g>`_
 
@@ -13,28 +13,27 @@ Quick Start
 ===========
 
 In order to build one of the sample apps, you need to set a few environment
-variables:
-```
-export BL60X_SDK_PATH=/path/to/this/repo
-export CONFIG_CHIP_NAME=bl602
-```
-Then go to the sample directory of interest and call `make`, for example:
-```
-cd customer_app/bl602_boot2
-make
-```
-Call
-```
-make CONFIG_TOOLPREFIX=riscv64-linux-gnu-
-```
+variables::
+
+    export BL60X_SDK_PATH=/path/to/this/repo
+    export CONFIG_CHIP_NAME=bl602
+
+Then go to the sample directory of interest and call `make`, for example::
+
+    cd customer_app/bl602_boot2
+    make
+
+Call ::
+
+    make CONFIG_TOOLPREFIX=riscv64-linux-gnu-
+
 for bypassing the bundled crosscompiler and using your distribution's own crosscompiler.
 
 
 There is a linker script (written in python) at `image_conf/flash_build.py`.
-To run this, you need to specify the application and the target, for example:
-```
-python3 flash_build.py bl602_boot2 bl602
-```
+To run this, you need to specify the application and the target, for example::
+
+    python3 flash_build.py bl602_boot2 bl602
 
 Hardware
 =========