docs: update node version support (#986)

Author: armano2

README.md

@@ -171,7 +171,7 @@ is room and need for improvement. The items on the roadmap should enhance `commi
 
 ## Version Support
 
-- Node.js [LTS](https://github.com/nodejs/LTS#lts-schedule) `>= 6`
+- Node.js [LTS](https://github.com/nodejs/LTS#lts-schedule) `>= 8`
 - git `>= 2.13.2`
 
 ## Related projects