Add missing Threads dependency to Config.cmake.in
Add missing Threads dependency to Config.cmake.in

Without this, systems that linked against Threads::Threads (namely
Linux) don't "just work" with find_package(SQLiteCpp), but instead
require you to find & link against Threads manually.

So this fixes that by finiding it for you, if it was used.

mc-server/SQLiteCpp,mc-server/SQLiteCpp,SRombauts/SQLiteCpp,SRombauts/SQLiteCpp,SRombauts/SQLiteCpp,mc-server/SQLiteCpp