chore: Add filtered pending PRs link to main page (#18854)

## Which issue does this PR close?

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- Closes #.

## Rationale for this change

I'm frustrated every time I need to apply a multifield filter to get a
list of PRs that ready to be reviewed, adding this filter to the main
page as the badge along with the PR number

The current PR filter:

- not draft
- not yet approved
- CI passed


<img width="128" height="44" alt="image"
src="https://github.com/user-attachments/assets/2a42f516-cb09-4aad-8d42-f9826e152f09"
/>


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## What changes are included in this PR?

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## Are these changes tested?

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## Are there any user-facing changes?

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Author: comphead

README.md

@@ -24,6 +24,7 @@
 [![Build Status][actions-badge]][actions-url]
 ![Commit Activity][commit-activity-badge]
 [![Open Issues][open-issues-badge]][open-issues-url]
+[![Pending PRs][pending-pr-badge]][pending-pr-url]
 [![Discord chat][discord-badge]][discord-url]
 [![Linkedin][linkedin-badge]][linkedin-url]
 ![Crates.io MSRV][msrv-badge]
@@ -39,6 +40,8 @@
 [commit-activity-badge]: https://img.shields.io/github/commit-activity/m/apache/datafusion
 [open-issues-badge]: https://img.shields.io/github/issues-raw/apache/datafusion
 [open-issues-url]: https://github.com/apache/datafusion/issues
+[pending-pr-badge]: https://img.shields.io/github/issues-search/apache/datafusion?query=is%3Apr+is%3Aopen+draft%3Afalse+review%3Arequired+status%3Asuccess&label=Pending%20PRs&logo=github
+[pending-pr-url]: https://github.com/apache/datafusion/pulls?q=is%3Apr+is%3Aopen+draft%3Afalse+review%3Arequired+status%3Asuccess+sort%3Aupdated-desc
 [linkedin-badge]: https://img.shields.io/badge/Follow-Linkedin-blue
 [linkedin-url]: https://www.linkedin.com/company/apache-datafusion/
 [msrv-badge]: https://img.shields.io/crates/msrv/datafusion?label=Min%20Rust%20Version