build: use es2018 as output

node 10.18.0 has full support of es2018. Specify that 10.18.0 is the minimium supported node version

Author: RebeccaStevens

package.json

@@ -112,5 +112,8 @@
     "typescript": {
       "optional": true
     }
+  },
+  "engines": {
+    "node": ">=10.18.0"
   }
 }

rollup.config.js

@@ -54,9 +54,7 @@ const cjs = {
   plugins: [
     rollupPluginNodeResolve(),
     rollupPluginCommonjs(),
-    rollupPluginTypescript({
-      tsconfigOverride: { compilerOptions: { target: "es5" } }
-    }),
+    rollupPluginTypescript(),
     rollupPluginJSON({
       preferConst: true
     })
@@ -77,9 +75,7 @@ const esm = {
   plugins: [
     rollupPluginNodeResolve(),
     rollupPluginCommonjs(),
-    rollupPluginTypescript({
-      tsconfigOverride: { compilerOptions: { target: "es2017" } }
-    }),
+    rollupPluginTypescript(),
     rollupPluginJSON({
       preferConst: true
     })

tsconfig.json

@@ -16,7 +16,7 @@
     "resolveJsonModule": true,
     "sourceMap": false,
     "strictNullChecks": true,
-    "target": "esnext",
+    "target": "es2018",
     "outDir": "js_out"
   },
   "include": ["src/**/*.ts"]