update html5 boilerplate urls

Author: joshbuchea

README.md

@@ -570,8 +570,8 @@ Minimum required xml markup for `browserconfig.xml`:
 
 ## Other Resources
 
-- 📖 [HTML5 Boilerplate Docs: The HTML](https://github.com/h5bp/html5-boilerplate/blob/master/dist/doc/html.md)
-- 📖 [HTML5 Boilerplate Docs: Extend and customize](https://github.com/h5bp/html5-boilerplate/blob/master/dist/doc/extend.md)
+- 📖 [HTML5 Boilerplate Docs: The HTML](https://github.com/h5bp/html5-boilerplate/blob/main/docs/html.md)
+- 📖 [HTML5 Boilerplate Docs: Extend and customize](https://github.com/h5bp/html5-boilerplate/blob/main/docs/extend.md)
 
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