TF-1018 Add Configuration guide for App Grid

docs/configuration/app_grid_configuration.md

@@ -0,0 +1,48 @@
+## Configuration for App Grid
+
+### Context
+- Team Mail is a service inside Twake Workspace which include other services
+- User need to access other services from Team Mail
+
+### How to config
+
+1. Add services to configuration file
+ 
+- Each service have the information:
+```
+    {
+      "appName": "Contacts",
+      "icon": "ic_contacts_app.svg",
+      "appLink": "https://openpaas.linagora.com/contacts/"
+    }
+```
+
+- All services must be added to the configuration file [configurations\app_dashboard.json](https://github.com/linagora/tmail-flutter/blob/master/configurations/app_dashboard.json)
+For example:
+```
+{
+  "apps": [
+    {
+      "appName": "Twake",
+      "icon": "ic_twake_app.svg",
+      "appLink": "http://twake.linagora.com/"
+    },
+    {
+      "appName": "App 1",
+      "icon": "ic_twake_app.svg",
+      "appLink": "http://twake.linagora.com/"  
+    },
+    ...
+  ]
+}
+```
+
+- `appName`: The name will be showed in App Grid
+- `icon`: Name of icon was added in `configurations\icons` folder
+- `appLink`: Service URL
+
+2. Enable it in [env.file](https://github.com/linagora/tmail-flutter/blob/master/env.file)
+```
+APP_GRID_AVAILABLE=supported
+```
+If you want to disable it, please change the value to `unsupported` or remove this from `env.file`