sfffe: add README

plugins/sfffe/README.md

+# "Search files for Front-End"
+
+This plugin adds a few functions for searching files used in Front-End web development.
+
+To use it, add `sfffe` to the plugins array in your zshrc file:
+```zsh
+plugins=(... sfffe)
+```
+
+**Requires:** `ack`
+
+## Functions
+
+- `ajs`: look for string in `.js` files.
+- `acss`: look for string in `.css` files.
+- `fjs`: search for `.js` files under the current working directory.
+- `fcss`: search for `.css` files under the current working directory.