chore: use Node 16

- run tests with 16 (and legacy 10)
- specify >10 in package.json
- specify 16 in nvmrc

.github/workflows/test.yml

@@ -9,7 +9,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [10.x, 12.x, 14.x]
+        node-version: [10.x, 16.x]
 
     steps:
     - uses: actions/checkout@v2

.nvmrc

@@ -1 +1 @@
-lts/*
+16

README.md

@@ -22,7 +22,7 @@ The server's capabilities can be expanded with the help of plugins that provide
 Detailed instructions for [installation on Raspberry Pi](https://github.com/SignalK/signalk-server-node/blob/master/raspberry_pi_installation.md)
 
 Prerequisites
-* Node.js version 10 or higher with npm installed
+* Node.js version 16 with latest npm installed (the server works for the time being on Node version >=10, but we are moving to the latest LTS version that is v16 in 9/2021)
 
 ## Use: Install from npm
 

package.json

@@ -64,7 +64,7 @@
   ],
   "license": "Apache-2.0",
   "engines": {
-    "node": "10"
+    "node": ">=10"
   },
   "dependencies": {
     "@signalk/server-admin-ui": "1.39.x",