Change the default branch name to use more inclusive language

[eatyourgreens]

Package

The whole repo.

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

GitHub removed the old default branch name, with its connotations of racism and slavery, in 2020. The monorepo still uses it, four years later.

Describe the solution you'd like

It would be a small, but inclusive, step to change the monorepo tooling over to using main.