docs: add link to standard library repository (#185)

Fixes #122 - adds missing link to https://github.com/goboscript/std
in the standard library documentation page

Author: Sendi0011

docs/standard-library.md

@@ -3,6 +3,8 @@
 The standard library is a collection of useful procedures, functions and macros that
 can be used in any goboscript project.
 
+**Repository:** <https://github.com/goboscript/std>
+
 ## Standard library headers
 
 Include a header using the `%include` directive.
@@ -18,4 +20,4 @@ the compiled project.
 
 There is no hand-written documentation currently, so refer to AI-generated documentation.
 
-<https://deepwiki.com/goboscript/std>
+<https://deepwiki.com/goboscript/std>