Upgrade dependencies, fix lint errors

* Upgrade to Marked 15
* Upgrade to ESLint 9 and typescript-eslint 8
* Stay on TypeScript 5.6 because of an issue with vue-tsc with TS 5.7:
  vuejs/language-tools#5018
  (and also because typescript-eslint doesn't officially support 5.7)

eslint.config.js

@@ -3,7 +3,6 @@ import vue from 'eslint-plugin-vue';
 import typescript from 'typescript-eslint';
 import prettier from 'eslint-config-prettier';
 import vueEslintParser from 'vue-eslint-parser';
-import typescriptEslintParser from '@typescript-eslint/parser';
 
 export default [
 	js.configs.recommended,
@@ -20,7 +19,7 @@ export default [
 			ecmaVersion: 2015,
 			parser: vueEslintParser,
 			parserOptions: {
-				parser: typescriptEslintParser,
+				parser: typescript.parser,
 				project: true,
 				extraFileExtensions: ['.vue'],
 				sourceType: 'module',