Add README

Description taken from https://blog.golang.org/go-fonts.

GoMono/README.rst

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+Go Mono for Powerline
+=====================
+
+:Font creator: Bigelow & Holmes
+:Source: https://go.googlesource.com/image
+:Patched by: `Anwar <https://github.com/AnwarShah>`_
+
+Go monospace font initially developed for testing go user interface toolkit. It 
+is being said that go source code looks particularly good when displayed in Go 
+fonts, with things like punctuation characters easily distinguishable and 
+operators lined up and placed consistently.