[Docs] Use absolute URL for nvm-sh#606 in README.md

Since markdown-link-check hasn't support relative links, to make the
test passed, move this link to use absolute URL so that we can introduce
the new test. cc tcort/markdown-link-check#10

Author: PeterDaveHello

README.md

@@ -752,7 +752,7 @@ my_alias        default        v10.22.0       v12.18.3      v14.8.0
 
 ## Compatibility Issues
 
-`nvm` will encounter some issues if you have some non-default settings set. (see [#606](/../../issues/606))
+`nvm` will encounter some issues if you have some non-default settings set. (see [#606](https://github.com/creationix/nvm/issues/606))
 The following are known to cause issues:
 
 Inside `~/.npmrc`: