Quick and dirty versioning script (#1305)

Summary:
Pull Request resolved: https://github.com/facebook/yoga/pull/1305

Made a quick script to set versions in manifests that currently exist. This should probably be stamped in more places, like the binary as well, but we don't do that right now. This does not update lockfiles for CocoaPods or JS, so those will need to be updated via an install after running this script.

A note on language: This repo already has too many toolchains, but I chose Python for this since it corresponds with the enum script, and we  can run it with no dependencies on macOS/Linux distros.

Reviewed By: cortinico

Differential Revision: D46662378

fbshipit-source-id: 74ab99eef137511f8ed2fd7d81335a0fa633caf5

Yoga.podspec

@@ -6,7 +6,7 @@
 
 Pod::Spec.new do |spec|
   spec.name = 'Yoga'
-  spec.version = '2.0.0-beta.1'
+  spec.version = '2.0.0'
   spec.license =  { :type => 'MIT', :file => "LICENSE" }
   spec.homepage = 'https://yogalayout.com/'
   spec.documentation_url = 'https://yogalayout.com/docs'