New Shadow module (#1507)

* circular gradient module

* Shadow module added

* fixed minor documentation error

* fixed small errors

* added test for shadow module

* updated shadow module to receive x and y inputs

* final shadow module with two inputs

* fixed test for shadow module

Co-authored-by: Harsh Khandeparkar <34770591+HarshKhandeparkar@users.noreply.github.com>
Co-authored-by: Jeffrey Warren <jeff@unterbahn.com>

src/modules/Shadow/index.js

@@ -0,0 +1,4 @@
+module.exports = [
+  require('./Module'),
+  require('./info.json')
+];