Post: write a small post about new dashboard

[humitos]

We want to write a small blog post communicating that we are making the new dashboard the default one. The goal of this blog post is to be simple, short and concrete (can be seen as a changelog entry). We will write another blog post in the future explaining the new features more in details.

• Related: https://github.com/readthedocs/readthedocs-ops/issues/1515#issuecomment-2304642514

[humitos]

I'm bumping the priority of this issue because we are pretty close to migrate all the domains to the new templates 🎉