Arbitrary module identifiers support

[rhysd]

TypeScript 5.6 supported arbitrary module identifiers.

declare const some_imports: unknown;
export { some_imports as "some imports" };

import { "some imports" as foo } from "./module.js";

• https://devblogs.microsoft.com/typescript/announcing-typescript-5-6/#support-for-arbitrary-module-identifiers4
• https://github.com/tc39/ecma262/pull/2154

Syntax highlighting for the export statement worked fine out-of-box but import statement didn't work (notice the string literal is not highlighted):

This PR fixes the syntax highlighting with renaming typescriptTypeBlock to typescriptImportBlock. The screenshot after the fix is:

I also updated the files in merged/*.vim.