feat: Add version headers to all responses

[ShibireX]

The version header is dynamically updated via npm_package_version, and appended to all other existing headers. By using a Fastify hook, we ensure that the version header gets featured in every proxy response.

[birme]

In general looks good. Just add a unit test for this and we are good.
Look at fastify.inject() for that

[birme]

The intention with the unit test is to test the implementation in server.ts. I don't really see that this does that?

[birme]

I'd prefer that you add the hook in the registerRoutes() function because then in the unit test it would be just a matter of doing something like:

describe('Chaos Stream Proxy server', () => {
  let app;
  beforeEach(() => {
    app = fastify();
    registerRoutes(app);
  });

  it.each([HLS_PROXY_MASTER, HLS_PROXY_MEDIA, SEGMENTS_PROXY_SEGMENT])('route %p contains x-version header', (route) => {
    const response = await app.inject(route);
    expect(response.headers).objectContaining(...)
  });
});

[birme]

Looks good now. Squash (using rebase) this PR into one single commit and I will merge it to main