Drop node 14.x, 15.x from tests

Author: antonmedv

.github/workflows/test.yml

@@ -13,7 +13,7 @@ jobs:
 
     strategy:
       matrix:
-        node-version: [14.x, 15.x, 16.x]
+        node-version: [16.x, 17.x]
 
     steps:
     - uses: actions/checkout@v2

README.md

@@ -31,9 +31,7 @@ gives sensible defaults.
 npm i -g zx
 ```
 
-### Requirement
-
-Node.js >= 14.13.1
+**Requirement**: Node version >= 16.0.0
 
 ## Documentation