Add GetModID as a Legacy v4 Native Function

[EggBanana123]

Just like the RSDKv4 PR,
Adds the v4 native function GetModID, which gets the mod ID of a specified mod via folder name

One use case could be;

CallNativeFunction2(GetModID, "ModFolder", 0)
temp0 = checkResult
CallNativeFunction2(GetModActive, temp0, 0)

if checkResult == true
...

to check whether a specific mod is enabled before running a patch for it