Update ddev instructions in README

[gilzow]

Describe the bug

If you have previously started ddev from this same template, you'll hit an error during ddev start that a project with this name already exists in a stopped state. To avoid that error, users need to update the name: property in .ddev/config.yaml

Include some logs

N/a

Reproducing

1. Clone repo (or start a new psh project)
2. follow readme for ddev
3. stop ddev
4. Clone this repo again or create another new psh project based on this repo
5. follow readme for ddev

Error:

Failed to get project(s): a project (web container) in exited state already exists for api that was created at /path/to/other/repo

Expected behavior

n/a

Your environment

n/a

Screenshots

No response

Additional context

No response