Documentation - Document integrations execution order troubleshooting tricks

[castarco]

Preamble

As I discovered while I was implementing support for deployments on Vercel, the order of execution of Astro integrations matters a lot.

At the time, I had to introduce some hacks to make it work for Vercel. This hack caused a noticeable regression for some users ( #140 ).

While the regression can be fixed, it's still possible that some users will keep struggling to combine many integrations.

Proposal

Because of that, I think that we should introduce a new page into our documentation to explain how to troubleshoot this specific kind of problem, providing them some useful resolution strategies.