SSL certificates can cause problems

In my case, after setting up `local-vip` and running the cert-build command as described in the README, I was unable to access my site: All browsers returned a `ERR_SSL_UNRECOGNIZED_NAME_ALERT`.

The `altis-proxy` docker container was also throwing errors like this:

```
21T19:54:25Z" level=error msg="Unable to add a certificate to the entryPoint \"https\" : unable to generate TLS certificate : tls: private key does not match public key"

time="2022-07-21T19:54:25Z" level=error msg="failed to load X509 key pair: tls: private key does not match public key"
```

Ultimately the following steps solved the problem _for me_ but they are not really generalizable at this time:

1. edit `vendor/humanmade/local-vip/.bin/build-cert.sh` to remove the line `mv ${DOMAIN}.crt ${PWD}/${DOMAIN}.crt` because it attempts to move a file to itself, an action which fails and halts the entire script
2. run `bash .bin/build-cert.sh nxs.local`
3. import the resulting `vendor/humanmade/local-vip/nxs.local.crt` into my OS via Keychain Access, and then tell my system to trust it
4. stop and restart my server and the altis-proxy docker container

This was caused by a couple things:

- The repo does not ship with any domain-specific keys
- It has instructions for adding keys generated by the above `bash` command
- This can lead to a situation where the wrong keys are imported (if the proxy isn't restarted)
- This whole process is very messy if it needs to be done every time someone instantiates `local-vip` for a new project

`local-server` more or less "just works" and creates every project on `altis.dev` (from my recollection--I may be wrong) so potentially this should be modified to do the same, with instructions for how to deviate from that, if necessary (and ideally with a more streamlined process).

My understanding is that the proxy and traefik can be used for this, but my grasp of both those things is very limited.

Additionally, the [script to build certs](https://github.com/humanmade/local-vip/blob/edf81e8e99c7d1905ac09615111a617a58b10c37/.bin/build-cert.sh) contains direct references to Nexstar. So far as I can tell these don't cause any problems on their own, but they should probably be removed.