The local development workflow should "just work" for most projects

**Is your feature request related to a problem? Please describe.**

The local development flow is what most devs expect when running the CMS locally, but it isn't enabled by default, and often requires manually starting a server. It's also not obvious in the UI when the local development is enabled.

**Describe the solution you'd like**

Local development should "just work" for popular workflows, and it should be obvious in the UI.

Issues should be created for each of the following:
- #3286: Make development mode obvious in UI
- Integrate dev server with gatsby-plugin-netlify-cms
- Integrate dev server with victor-hugo

**Describe alternatives you've considered**

**Additional context**