Update required Node.js version to 18 and add .nvmrc file (#1555)

.changeset/sour-teachers-collect.md

@@ -0,0 +1,5 @@
+---
+"@tabler/core": patch
+---
+
+Update required Node.js version to 18 and add `.nvmrc` file

.nvmrc

@@ -0,0 +1 @@
+18

package.json

@@ -45,7 +45,7 @@
     "url": "https://github.com/sponsors/codecalm"
   },
   "engines": {
-    "node": ">=16"
+    "node": ">=18"
   },
   "files": [
     "dist/**/*",