feat: HTTP + HTTPS proxy support (#139)

Co-authored-by: Hiroki Osame <hiroki.osame@gmail.com>

src/utils/config.ts

@@ -51,6 +51,15 @@ const configParsers = {
 
 		return parsed;
 	},
+	proxy(url?: string) {
+		if (!url || url.length === 0) {
+			return undefined;
+		}
+
+		parseAssert('proxy', /^https?:\/\//.test(url), 'Must be a valid URL');
+
+		return url;
+	},
 } as const;
 
 type ConfigKeys = keyof typeof configParsers;