feat: add request variable

packages/hoppscotch-common/locales/en.json

@@ -239,6 +239,7 @@
     "pending_invites": "There are no pending invites for this team",
     "profile": "Login to view your profile",
     "protocols": "Protocols are empty",
+    "request_variables": "This request does not have any request variables",
     "schema": "Connect to a GraphQL endpoint to view schema",
     "secret_environments": "Secrets are not synced to Hoppscotch",
     "shared_requests": "Shared requests are empty",
@@ -560,6 +561,7 @@
     "raw_body": "Raw Request Body",
     "rename": "Rename Request",
     "renamed": "Request renamed",
+    "request_variables": "Request variables",
     "run": "Run",
     "save": "Save",
     "save_as": "Save as",