Moved md documents from doc/ to docs/.

The HTML output is docs/html folder. So, having doc/ is redundant.

Author: suikan4github

.gitignore

@@ -36,4 +36,3 @@ build/
 .vscode/
 html/
 *.bak
-docs/html

README.md

@@ -10,11 +10,11 @@ These classes are provided in this version.
 
 | class                                                  | Description |
 |---------------------------------                       |----------------------------- |
-| ::rpp_driver::[SdkWrapper](doc/sdkwrapper.md)         | Wrapper class of Pico SDK    |
-| ::rpp_driver::[GpioBasic](doc/gpiobasic.md)           | Basic GPIO controller        |
-| ::rpp_driver::[I2cMaster](doc/i2cmaster.md)           | I2C Master controller        |
-| ::rpp_driver::[I2sSlaveDuplex](doc/duplexslavei2s.md) | Polling based PIO I2S driver |
-| ::rpp_driver::[Adau1361](doc/adau1361.md)             | Audio CODEC driver           |
+| ::rpp_driver::[SdkWrapper](docs/sdkwrapper.md)         | Wrapper class of Pico SDK    |
+| ::rpp_driver::[GpioBasic](docs/gpiobasic.md)           | Basic GPIO controller        |
+| ::rpp_driver::[I2cMaster](docs/i2cmaster.md)           | I2C Master controller        |
+| ::rpp_driver::[I2sSlaveDuplex](docs/duplexslavei2s.md) | Polling based PIO I2S driver |
+| ::rpp_driver::[Adau1361](docs/adau1361.md)             | Audio CODEC driver           |
 
 
 ## How to obtain this project