docs(README.md): Add description

README.md

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 # wp-env-port-stamp
 
-npm package writes an .wp-env.json file with custom ports.
+**TL;DR:** *wp-env-port-stamp* is a npm package who generates an *.wp-env.json* file with custom ports for your *wp-env* envirenment.
+
+## Background
+
+If you work with different docker envirenments at the same time you need to manage the ports. *wp-env* use port 8888 per default. If this port is already in use by another project then you have an problemen. But the solution is easy: Just change the ports...
+
+*wp-env-prt-stamp* generates every time an new port adress - more or less - randomly. When the package is called, it creates a file *.wp-env.json* in the directory where it was called. With this *.wp-env.json* file you can customize the WordPress installation. In our case are dynamic renderered port numbers.
+
+The port number will be generatated from the current JavaScript date - the time in miliseconds since the ECMAScript epoch. We take the last 4 numbers of this time as the port number. This solution my not be perfekt but good enough for your dayly local web development with a handfull docker instances. :-)
+
+## Install/Remove
+
+Install the package global on your local computer:
+
+```
+npm i -g wp-env-port-stamp
+```
+
+To remove the packe:
+
+```
+npm uninstall -g wp-env-port-stamp
+```
+
+## Usage
+
+1. Go in your local dev envirenment to your plugin, theme or block root directory or wherever you want to start *wp-env*.
+2. Call the package: `wp-env-port-stamp`
+3. The file is generated. You can start now with `wp-env`
+
+Normaly you only need to call the package for the first time in an new project. Later just start directly *wp-env*.
+
+**Attention:** If there is already existing *.wp-env.json* file, *wp-env-port-stamp* will overwrite it! (There will be an improvement to this later).