JetBrains.gitignore: add ignore for the HTTP Client's private environment

- documentation regarding env config files: https://www.jetbrains.com/help/idea/exploring-http-syntax.html#example-working-with-environment-files
- rename Rest Client to HTTP Client

Author: kaznovac

Global/JetBrains.gitignore

@@ -70,8 +70,9 @@ crashlytics.properties
 crashlytics-build.properties
 fabric.properties
 
-# Editor-based Rest Client
+# Editor-based HTTP Client
 .idea/httpRequests
+http-client.private.env.json
 
 # Android studio 3.1+ serialized cache file
 .idea/caches/build_file_checksums.ser