Added class and os alternates

.oh-my-zsh/plugins/textastic/README.md

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+## textastic
+
+Plugin for Textastic, a text and code editor for Mac OS X
+
+### Requirements
+
+ * [Textastic](https://www.textasticapp.com/mac.html)
+
+### Usage
+
+ * If `tt` command is called without an argument, launch Textastic
+
+ * If `tt` is passed a directory, cd to it and open it in Textastic
+
+ * If `tt` is passed a file, open it in Textastic