Add README-branch to make v2.2-latest appear as a separate line in the network viewer

dpvc · dpvc · commit 90cd96cd53c2 · 2013-05-17T05:56:34.000-04:00
diff --git a/README-branch.txt b/README-branch.txt
@@ -0,0 +1 @@
+This is release branch v2.2 of MathJax.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+This is release branch v2.2 of MathJax.`