chore: fix typo in README.md (#246)

README.md

@@ -662,7 +662,7 @@ yarn
 
 3. Within the better-docs folder run the gulp script. It will regenerate documentation every time you change something.
 
-It supports following EVN variables:
+It supports following ENV variables:
 
 * `DOCS_COMMAND` - a command in your root repo which you use to generate documentation: i.e. `DOCS_COMMAND='jsdoc -c jsdoc.json'` or `npm run docs` if you have `docs` command defined in `package.json` file
 * `DOCS_OUTPUT` - where your documentation is generated. It should point to the same folder your jsdoc `--destination` conf. But make sure that it is relative to the path where you cloned `better-docs`.