feat(translation): add Estonian default translation

[chirbard]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes #0000) and the maintainers have approved on my working plan.

Motivation

Add Estonian default translations.

Related issues/PRs

#3526

[netlify]

✅ [V2]

Name	Link
🔨 Latest commit	5c8f5b2
🔍 Latest deploy log	https://app.netlify.com/sites/docusaurus-2/deploys/66a265d70868c800081e24d6
😎 Deploy Preview	https://deploy-preview-10339--docusaurus-2.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[github-actions]

⚡️ Lighthouse report for the deploy preview of this PR

URL	Performance	Accessibility	Best Practices	SEO	Report
/	🟠 73	🟢 98	🟢 96	🟢 100	Report
/docs/installation	🟠 61	🟢 97	🟢 100	🟢 100	Report
/docs/category/getting-started	🟠 74	🟢 100	🟢 100	🟠 86	Report
/blog	🟠 68	🟢 96	🟢 100	🟠 86	Report
/blog/preparing-your-site-for-docusaurus-v3	🔴 48	🟢 92	🟢 100	🟢 100	Report
/blog/tags/release	🟠 69	🟢 96	🟢 100	🟠 86	Report
/blog/tags	🟠 75	🟢 100	🟢 100	🟠 86	Report

[slorber]

Thanks, LGTM 👍