Revise README to include links to docs for better guidance

[josh-wong]

Description

This PR updates the root-level README to guide visitors of this repository to beginner-level documentation on the ScalarDL docs site. By listing specific docs and short explanations, we can help guide visitors to docs that may help them get started with using ScalarDL.

Related issues and/or PRs

For consistency, I've updated the README in the scalar-labs/scalardb repository:

• Revise README to include links to docs for better guidance scalardb#2611

Changes made

• Revised the Docs section to include links to getting-started tutorials, configurations, and features on the docs site.
• Added a link to the ScalarDL overview page to the end of the introductory paragraph.

Checklist

The following is a best-effort checklist. If any items in this checklist are not applicable to this PR or are dependent on other, unmerged PRs, please still mark the checkboxes after you have read and understood each item.

• I have commented my code, particularly in hard-to-understand areas. N/A
• I have updated the documentation to reflect the changes. N/A
• I have considered whether similar issues could occur in other products, components, or modules if this PR is for bug fixes. N/A
• Any remaining open issues linked to this PR are documented and up-to-date (Jira, GitHub, etc.). N/A
• Tests (unit, integration, etc.) have been added for the changes. N/A
• My changes generate no new warnings. N/A
• Any dependent changes in other PRs have been merged and published. N/A

Additional notes (optional)

N/A

Release notes

N/A

[kota2and3kan]

Thank you for the updates!
I left minor suggestions.
Please take a look when you have time! 🙇‍♂️

[kota2and3kan]

LGTM! Thank you!

[jnmt]

LGTM, thank you! I left a minor suggestion that doesn't block merging the PR.

[choplin]

LGTM!

[feeblefakie]

LGTM! Thank you!
I left a comment about what to show.