Add an RBI file for PyCall

lib/pycall-setup.rbi

@@ -0,0 +1,15 @@
+# typed: true
+
+module InfluxDBClient3; end
+
+module PyCall
+  def self.init(*args); end
+
+  module Import
+    def self.pyfrom(*args); end
+
+    def self.import(*args); end
+  end
+
+  class PyError; end # rubocop:disable Lint/EmptyClass
+end