docs(README): added notice about Bitbucket sourcemaps
docs(README): added notice about Bitbucket sourcemaps

bryanbecker/screeps-typescript-starter,KeithHanson/screeps-typescript,Sean-Brown/screeps-typescript-starter,Sean-Brown/screeps-typescript-starter,Adirelle/typescreeps,boriswintein/Empire,tinnvec/aints,Adirelle/typescreeps,KeithHanson/screeps-typescript,bryanbecker/screeps-typescript-starter,tinnvec/aints