fix broken links in readme.md for bigseries (#2997)

keyboards/bigseries/readme.md

@@ -12,4 +12,4 @@ Make example for this keyboard (after setting up your build environment):
 
     make bigseries:default
 
-See [build environment setup](https://docs.qmk.fm/build_environment_setup.html) then the [make instructions](https://docs.qmk.fm/make_instructions.html) for more information.
+See [build environment setup](https://docs.qmk.fm/install-build-tools) then the [make instructions](https://docs.qmk.fm/build-compile-instructions) for more information.