golang.org: fill searched value in search input after submit

[jan25]

Fixes golang/go#40218

Auto fill previous searched value in search box at https://golang.org/

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Patch Set 1:

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Next steps:
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[gopherbot]

Message from Go Bot:

Patch Set 1:

Congratulations on opening your first change. Thank you for your contribution!

Next steps:
A maintainer will review your change and provide feedback. See
https://golang.org/doc/contribute.html#review for more info and tips to get your
patch through code review.

Most changes in the Go project go through a few rounds of revision. This can be
surprising to people new to the project. The careful, iterative review process
is our way of helping mentor contributors and ensuring that their contributions
have a lasting impact.

---

Please don’t reply on this GitHub thread. Visit golang.org/cl/243400.
After addressing review feedback, remember to publish your drafts!