Change tsconfig.build.json to JSONC

To reduce the number of top-level files.

`.jsonc` file extension is actually most accurate for tsconfig file: it
allows comments regardless of a file extension.

package.json

@@ -42,7 +42,7 @@
 		"vitest": "^2.1.5"
 	},
 	"scripts": {
-		"build": "tsc -p tsconfig.build.json",
+		"build": "tsc -p tsconfig.build.jsonc",
 		"test": "vitest",
 		"prepare": "npm run build"
 	}

tsconfig.build.jsonc

@@ -0,0 +1,13 @@
+// TypeScript config file. This one is for generating release JS files.
+//
+// SPDX-FileCopyrightText: 2024 Shota FUJI <pockawoooh@gmail.com>
+// SPDX-License-Identifier: Apache-2.0
+{
+	"extends": "./tsconfig.json",
+	"compilerOptions": {
+		"outDir": "esm/es2020",
+		"noEmit": false,
+		"declaration": true
+	},
+	"include": ["./src/plugin.ts"]
+}