Added Docker CI/CD

* Added CI/CD to create Docker image and updated README * I also optimized the project's Docker images. This optimization reduced the compressed package size by 42 MB. [Before](https://hub.docker.com/layers/andromeda606/youtube-operational-api/1a2e111/images/sha256-addb66d41799f03584a74b3b9c5406675ed5a21cbf87065e6d91fea360e6e949) -> [After](https://hub.docker.com/layers/andromeda606/youtube-operational-api/74b0d4c/images/sha256-040ebd22640b2bc71cebe39baef63b7e299aa512ecb89c6ff733c46940e3fb75) ## What to do First, you need to generate a secret key. You can generate tokens using the repository owner's username via this link: [https://app.docker.com/accounts/benjaminloison/settings/personal-access-tokens](https://app.docker.com/accounts/benjaminloison/settings/personal-access-tokens) Then click on the link: [https://github.com/Benjamin-Loison/YouTube-operational-API/settings/secrets/actions](https://github.com/Benjamin-Loison/YouTube-operational-API/settings/secrets/actions) and create the DOCKER_USERNAME and DOCKER_TOKEN parameters. Then confirm this MR. From this point on, the main branch is assumed to be the stable branch. We may want to change this. Related to #336