Fix one more mention of Node.js 8.9

Author: stasm

README.md

@@ -78,8 +78,7 @@ Hacking on `fluent.js` is easy! To quickly get started clone the repo:
     $ git clone https://github.com/projectfluent/fluent.js.git
     $ cd fluent.js
 
-You'll need node.js 8 LTS (v8.9.0 and up). Older 8.x versions and 7.x
-versions have been reported to work as well. node.js 6.x is not supported.
+You'll need at least Node.js 10 LTS. Older versions are not supported.
 
 Install the build tools used by all packages (Babel, Rollup, Mocha etc.):
 

babel_config.js

@@ -14,7 +14,7 @@ export default {
           "Safari >= 10.1",
           "iOS >= 10.3",
         ],
-        node: "8.9",
+        node: "10.0.0",
       },
       exclude: [
         // Exclude regeneratorRuntime explicitly because babel-preset-env