[CT-2870] [Bug] Incorrect examples in docker README

[jamezrin]

Is this a new bug in dbt-core?

• I believe this is a new bug in dbt-core
• I have searched the existing issues, and I could not find an existing issue for this bug

Current Behavior

The README file located in the directory for the Dockerfile has incorrect commands and inconsistent spacing between arguments.

• The command indicated in "Running an image in a container" is missing a newline escape
• There are two whitespaces before the --target flag in the examples and between other parameters
• Markdown script end markers are indented wrong
• Unnecessary newline escapes in two of the commands suggested

Expected Behavior

The README should provide commands that are functional and the style for the shell script should be consistent within the README file.

Steps To Reproduce

For example, execute the command for "Running an image in a container" as indicated by the README file

Relevant log output

N/A

Environment

N/A

Which database adapter are you using with dbt?

No response

Additional Context

No response