Permission issues on conf directory

[klpanagi]

Describe the bug

The Dockerfile does not set permissions for the /usr/src/app/conf/ directory, as with other dirs (https://github.com/hummingbot/gateway/blob/development/Dockerfile#L36), thus it causes gateway to crash on startup due to access error on that path.

This does not happen when the gateway-create.sh script is used because the permissions are set by the script, thus it is not a generic solution. The Dockerfile should set these permissions, thus making it possible to use other deployment schemas, other than the gateway-create.sh script. Such cases include compose and the usage of docker volumes.

Discord discussion: https://discord.com/channels/530578568154054663/1004143639733215392/1079418334199685120

Steps To Reproduce

Start gateway via docker without the gateway-create.sh script.

Release version

1.13.0 / development branch

Discord username: klpanagi