Add mise.toml and pin Node LTS

- mise.toml with node = "24.15.0" (current LTS)
- package.json: packageManager = "npm@11.12.1", engines.node >= 24.15.0

mise.toml

@@ -0,0 +1,2 @@
+[tools]
+node = "24.15.0"

package.json

@@ -2,6 +2,10 @@
   "name": "remotely-save",
   "version": "0.5.25",
   "description": "This is yet another sync plugin for Obsidian app.",
+  "packageManager": "npm@11.12.1",
+  "engines": {
+    "node": ">=24.15.0"
+  },
   "scripts": {
     "dev2": "node esbuild.config.mjs --watch",
     "build2": "tsc -noEmit -skipLibCheck && node esbuild.config.mjs production",