feat: Extract and expose timestamps from query results.

[hoophalab]

Description

This PR

1. extracts timestamp from the log data using the column-metadata endpoint;
2. updates README.md to explain the new features.

Checklist

• The PR satisfies the contribution guidelines.
• This is a breaking change and that has been indicated in the PR title, OR this isn't a
  breaking change.
• Necessary docs have been updated, OR no docs need to be updated.

Validation performed

Following the new instructions in README.md, logs are displayed correctly in "Explore". The user don't need to add transformations and extract the timestamps.

[hoophalab]

@coderabbitai Can you review this PR?

[junhaoliao]

matches my understanding of the implementation in y-scope/clp#1788

the rest lgtm