Add missing hints for Lua #438

Values hints

Use this emmylua feature : https://emmylua.github.io/annotations/string_literal_type.html to provide hints where possible (enums are a good candidate)

Also see https://github.com/sumneko/lua-language-server/wiki/Annotations#param (section "Custom Type Parameter") for a good example

For example, for functions taking a obe.transform.Units parameter, we could provide this following hint :

--- Return an UnitVector with the converted values (x, y) to the Unit you want.
---
---@param p_unit obe.transform.Units | obe.transform.Units.ViewPercentage | obe.transform.Units.ScenePixels #An enum value from Transform::Units
---@return obe.transform.UnitVector
function obe.transform._UnitVector:to(p_unit) end

Operator overload hints

See https://github.com/sumneko/lua-language-server/wiki/Annotations#operator for more details

All tasks descrived above should be implemented in Obidog