Add .bsp directory to SBT.gitignore

Since sbt 1.4.0 on every bootstrap sbt will create `.bsp/sbt.json` file that is environment specific.

Reference: https://contributors.scala-lang.org/t/build-server-protocol-in-sbt/4234

Global/SBT.gitignore

@@ -10,3 +10,4 @@ project/plugins/project/
 .history
 .cache
 .lib/
+.bsp/