Add npm instructions to Readme

Author: AntonPetrov

README.md

@@ -66,10 +66,19 @@ srpdb        |
 tair         |
 tmrna-website|
 wormbase     |
- 
- 
+
 ## Developer details
 
+### Local development
+
+1. `npm install`
+
+2. `npm run serve` to start a server on http://localhost:8080/
+
+3. `npm run build` to generate a new distribution.
+
+### Notes
+
 This embed is implemented as a Web Component, wrapping a piece of code in React/Redux.
 
 Being a Web Component, it isolates CSS styles from the main page to avoid clash of styles with it.