Add ScalarDL 3.10 docs; move ScalarDL 3.9 docs to dedicated version folder

[josh-wong]

Caution

This PR can be merged after ScalarDL 3.10 has been officially released.

Description

This PR moves the ScalarDL 3.9 docs to a versioned folder and adds ScalarDB 3.10 docs to the docs folder as the latest version.

Related issues and/or PRs

N/A

Changes made

• English docs
  • Moved 3.9 docs to the versioned_docs/version-3.9 folder.
  • Added 3.10 docs to the docs folder, which is where the latest version of English docs lives.
  • Added release notes.
  • Updated the Release Support Policy.
• Japanese docs
  • Moved 3.9 docs to the i18n/versioned_docs/ja-jp/docusaurus-plugin-content-docs/version-3.9 folder.
  • Added 3.10 docs to the *i18n/versioned_docs/ja-jp/docusaurus-plugin-content-docs/current folder, which is where the latest version of Japanese docs lives.
  • Added release notes.
  • Updated the Release Support Policy.
• Created a dedicated sidebar navigation for 3.9 (versioned_sidebars/version-3.9-sidebars.json)3.9 version sidebar from sidebars.js to 3.9.json andGenerated sidebarsMoved docs for 3.9 into a version folder, according to the Docusaurus versioning instructions.
• Added an announcement to the top of the docs site about the 3.10 release

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 updated the side navigation as necessary.
• I have commented my code, particularly in hard-to-understand areas.
• I have updated the documentation to reflect the changes.
• Any remaining open issues linked to this PR are documented and up-to-date (Jira, GitHub, etc.).
• My changes generate no new warnings.
• Any dependent changes in other PRs have been merged and published.

Additional notes (optional)

N/A

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