Adding Mailhog Support

[SirLouen]

Adding support for a mailhog container on demand with the env variable: LOCAL_MAILHOG

Patch Testing instructions:

1. Change LOCAL_MAILHOG=false to LOCAL_MAILHOG=true in your .env file
2. Run your docker environment as usual npm run env:start
3. You test if your mailhog instance is running with either: A) Go to http://localhost:8025/ B) You can run in your wordpress-develop container

docker exec -it  wordpress-develop-php-1 openssl s_client -connect mailhog:1025

And it might result in something like:

CONNECTED(00000003)
135865530688832:error:1408F10B:SSL routines:ssl3_get_record:wrong version number:../ssl/record/ssl3_record.c:331:
---
no peer certificate available
---
No client certificate CA names sent
---
SSL handshake has read 5 bytes and written 283 bytes
Verification: OK
---
New, (NONE), Cipher is (NONE)
Secure Renegotiation IS NOT supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
Early data was not sent
Verify return code: 0 (ok)

C) You can do further tests, like sending an email with a plugin that uses the local mailhog hostname For example this one: https://github.com/SirLouen/amazon-s3-email-testing/archive/refs/tags/1.0.0.zip

Trac ticket: https://core.trac.wordpress.org/ticket/63135

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