chore(README): grafana support matrix (#7)

README.md

@@ -1,10 +1,24 @@
 # grafana-pdf-exporter
+
 Export a Grafana dashboard as PDF
 
-Emails (exported dashboards) can be sent using SendGrid, in order to do this, one has to set FROM_NAME, FROM_EMAIL and SENDGRID_API_KEY environment variables.  
+## How to run
+
+Exported dashboards can be sent using SendGrid, in order to do this, one has to set these environment variables:
+- FROM_NAME
+- FROM_EMAIL
+- SENDGRID_API_KEY
 
+```sh
 sh sendgridSendEmail.sh -t 'to1@gmail.com;to2@gmail.com'  -s 'FINAL SCRIPT' -o '\<p\>Email body goes here\<\/p\>' -a '/tmp/test.sh;/tmp/test2.sh'
+```
 
-Thanks to @salv for the original nodejs implementation
+## Supported Grafana versions
 
+| Release   | Grafana versions |
+| :-------- | :--------------: |
+| v1.7.0    | >= 8             |
 
+## Contribution
+
+Thanks to @salv for the original nodejs implementation