#1 Added README.md, checkstyle and Github Actions

[IlyaLisov]

PR-Codex overview

This PR adds new functionality and improves code quality. Notable changes include:

Detailed summary

• Updated method signatures to use final keyword where appropriate
• Added Docker build and push workflow
• Added Maven build workflow
• Added Checkstyle suppression file
• Improved exception handling and error messages
• Improved security expressions
• Improved DTO validation
• Improved file and bucket handling for image uploads
• Improved code readability and maintainability

The following files were skipped due to too many changes: src/main/java/com/example/tasklist/service/impl/ImageServiceImpl.java, src/main/java/com/example/tasklist/web/security/expression/CustomSecurityExceptionHandler.java, README.md, src/main/java/com/example/tasklist/service/impl/TaskServiceImpl.java, src/main/java/com/example/tasklist/web/security/JwtTokenFilter.java, pom.xml, src/main/java/com/example/tasklist/web/dto/user/UserDto.java, src/main/java/com/example/tasklist/web/controller/UserController.java, src/main/java/com/example/tasklist/web/security/expression/CustomMethodSecurityExpressionRoot.java, src/main/java/com/example/tasklist/service/impl/UserServiceImpl.java, src/main/java/com/example/tasklist/config/ApplicationConfig.java, src/main/java/com/example/tasklist/web/security/JwtTokenProvider.java, src/main/java/com/example/tasklist/web/controller/ControllerAdvice.java

✨ Ask PR-Codex anything about this PR by commenting with /codex {your question}