[FL-1906] Documentation: add Doxyfile, prepare sources for doxygen. (#741)

* Documentation: add Doxyfile, prepare sources for doxygen.

* Update ReadMe and remove obsolete CLA

* Add contribution guide

* Contributing: update text

* Correct spelling

firmware/targets/furi-hal-include/furi-hal-delay.h

@@ -1,23 +1,39 @@
+/**
+ * @file furi-hal-delay.h
+ * Delay HAL API
+ */
+
 #pragma once
+
 #include "main.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
-/** Init DWT */
+/** Init DWT
+ */
 void furi_hal_delay_init(void);
 
-/**
- * Delay in milliseconds
- * @warning Cannot be used from ISR
+/** Delay in milliseconds
+ * @warning    Cannot be used from ISR
+ *
+ * @param[in]  milliseconds  milliseconds to wait
  */
 void delay(float milliseconds);
 
-/** Delay in microseconds */
+/** Delay in microseconds
+ *
+ * @param[in]  microseconds  microseconds to wait
+ */
 void delay_us(float microseconds);
 
-/** Get current millisecond */
+/** Get current millisecond
+ * 
+ * System uptime, pProvided by HAL, may overflow.
+ *
+ * @return     Current milliseconds
+ */
 uint32_t millis(void);
 
 #ifdef __cplusplus