Drop support for Node.js v10 in favour of Node.js v12

- update tsconfig
- set required node version based on https://node.green/#ES2020

Author: Pytal

package.json

@@ -37,7 +37,7 @@
     "lib"
   ],
   "engines": {
-    "node": ">=v10.24.1"
+    "node": ">=12.10.0"
   },
   "repository": "github:Pytal/deploy-env",
   "license": "MIT"

tsconfig.json

@@ -1,7 +1,7 @@
 {
   "compilerOptions": {
-    "target": "es2018",  // Node.js v10
-    "lib": ["es2018"],   // https://github.com/microsoft/TypeScript/wiki/Node-Target-Mapping
+    "target": "es2019",  // Node.js v12 config based on community repo https://github.com/tsconfig/bases#node-12-tsconfigjson
+    "lib": ["es2019", "es2020.promise", "es2020.bigint", "es2020.string"],   // Official target mapping https://github.com/microsoft/TypeScript/wiki/Node-Target-Mapping
     "module": "commonjs",
     "outDir": "lib",
     "declaration": true,