Port the source code to TypeScript

etc/eslint.js

@@ -1,5 +1,6 @@
 import {join} from "node:path";
 import js from "@eslint/js";
+import globals from "globals";
 import ts from "typescript-eslint";
 
 export default ts.config(
@@ -8,6 +9,9 @@ export default ts.config(
 	...ts.configs.stylisticTypeChecked,
 	{
 		languageOptions: {
+			globals: {
+				...globals.nodeBuiltin
+			},
 			parserOptions: {
 				project: "tsconfig.json",
 				tsconfigRootDir: join(import.meta.dirname, "..")
@@ -79,7 +83,7 @@ export default ts.config(
 			"no-implicit-globals": "error",
 			"no-implied-eval": "error",
 			"no-inline-comments": "off",
-			"no-invalid-this": "error",
+			"no-invalid-this": "off",
 			"no-iterator": "error",
 			"no-label-var": "error",
 			"no-labels": "error",

gulpfile.js

@@ -2,10 +2,13 @@ import {cp, readFile, writeFile} from "node:fs/promises";
 import {EOL} from "node:os";
 import {env} from "node:process";
 import {deleteAsync} from "del";
-import {$} from "execa";
+import {execa} from "execa";
 import gulp from "gulp";
 import pkg from "./package.json" with {type: "json"};
 
+// Runs a command.
+const $ = execa({preferLocal: true, stdio: "inherit"});
+
 // Builds the project.
 export async function build() {
 	await $`tsc --project src/tsconfig.json`;