Possible typo when handling `workspace.library`

[Here](https://github.com/LuaLS/lua-language-server/blob/e930179bbd6b3eb26721a676303e0e27cdb29290/script/workspace/workspace.lua#L181) we handle `Lua.workspace.library`, but unlike the other paths, we index `debug` (the global) and add to it, instead of `pattern`.

This looks like it is almost definitely a typo.

Start in script/workspace/workspace.lua around line 181 and compare the workspace.library handling with the other paths nearby. Verify whether pattern should be indexed instead of debug, then confirm that workspace.library handling behaves consistently with those paths.

Written by the indexing model from the issue text.