Update docs

Author: vascocosta

docs/reference.md

@@ -11,11 +11,8 @@ Explore the standard library functions available in GluonScript.
 ## Module `core`
 
 [fn append(list: List, element: Any): List](https://gluonscript.org/reference.html#fn-appendlist-list-element-any-list)
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 [fn import(file: String): Record](https://gluonscript.org/reference.html#fn-importfile-string-record)
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 [fn len(list: List): Int](https://gluonscript.org/reference.html#fn-lenlist-list-int)
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 [fn slice(list: List, start: Int, end: Int): List](https://gluonscript.org/reference.html#fn-slicelist-list-start-int-end-int-list)
 
 ## Module `conv`