examples: add Interesting snippet tags to examples and link in Readme.md

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

README.md

@@ -26,8 +26,24 @@ C API Modules        | C++ API Classes
  @ref maa.h "maa"    | @ref maa.h "maa"
 </center>
 
+### Hello Maa
+@snippet hellomaa.c Interesting
+
+### Basic GPIO
 @snippet gpio_read6.c Interesting
 
+### Basic PWM
+@snippet cycle-pwm3.c Interesting
+
+### Basic I2C
+@snippet analogin_a0.c Interesting
+
+### Basic AIO
+@snippet analogin_a0.c Interesting
+
+### Basic SPI
+@snippet spi_mcp4261.c Interesting
+
 ## Supported platforms
 
 - Galileo (Fab D)