Add readme for injection

README.md

@@ -27,6 +27,7 @@ View the changelog [here](https://github.com/jiahaog/nativefier/blob/master/Hist
 
 - Automatically retrieves the correct icon and app name
 - Flash Support (Needs Testing)
+- Javascript and CSS injection
 
 ## Installation
 
@@ -252,6 +253,20 @@ By default, nativefier will automatically try to determine the location of your
 
 From my experience, it might be helpful to pass the `--insecure` flag if you are using nativefied flash apps, as some `https` websites tend to serve flash insecurely.
 
+#### [inject]
+
+```
+--inject <value>
+```
+
+Allows you to inject a javascript or css file. This command can be run multiple times to inject the files.
+
+Example:
+
+```bash
+$ nativefier http://google.com --inject ./some-js-injection.js --inject ./some-css-injection.css ~/Desktop
+```
+
 ## Programmatic API
 
 You can use the Nativefier programmatic API as well.