fix links for read the docs (#4293)

* fix links for read the docs

* fix typo

fix typo in link

doc/faq/a02-my-esp-crashes.rst

@@ -83,7 +83,7 @@ is wrong, it restarts itself to tell you about it.
 There are two typical scenarios that trigger ESP restarts:
 
 -  **Exception** - when code is performing `illegal
-   operation <https://github.com/esp8266/Arduino/blob/master/doc/exception_causes.rst>`__,
+   operation <../exception_causes.rst>`__,
    like trying to write to non-existent memory location.
 -  **Watchdog** - if code is `locked
    up <https://en.wikipedia.org/wiki/Watchdog_timer>`__ staying too long
@@ -104,7 +104,7 @@ Typical restart because of exception looks like follows:
    Exception cause decoding
 
 Start with looking up exception code in the `Exception Causes
-(EXCCAUSE) <https://github.com/esp8266/Arduino/blob/master/doc/exception_causes.rst>`__
+(EXCCAUSE) <../exception_causes.rst>`__
 table to understand what kind of issue it is. If you have no clues what
 it's about and where it happens, then use `Arduino ESP8266/ESP32
 Exception Stack Trace

doc/faq/a04-board-generic-is-unknown.rst

@@ -54,15 +54,15 @@ follows:
     Error compiling for board Generic ESP8266 Module.
 
 Below is an example messages for
-`WeMos <https://github.com/esp8266/Arduino/blob/master/doc/boards.rst#wemos-d1>`__:
+`WeMos <../boards.rst#wemos-d1-r2-mini>`__:
 
 ::
 
     Board d1_mini (platform esp8266, package esp8266) is unknown
     Error compiling for board WeMos D1 R2 & mini.
 
-... and another one for `Adafruit
-HUZZAH <https://github.com/esp8266/Arduino/blob/master/doc/boards.rst#adafruit-huzzah-esp8266-esp-12>`__:
+... and another one for `Adafruit Feather
+HUZZAH <../boards.rst#adafruit-feather-huzzah-esp8266>`__:
 
 ::