search: increase priority for full (sub)title match when searching

[marxin]

Describe the bug

When searching with an exact match of a (sub)title, the result should be shown at the very top. Example: https://www.sphinx-doc.org/en/master/search.html?q=More+topics+to+be+covered

As seen the result is shown as 3rd:

It's defined in quickstart.rst as

More topics to be covered
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How to Reproduce

Use the current docs.

Expected behavior

No response

Your project

Sphinx

Screenshots

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OS

All

Python version

any

Sphinx version

any

Sphinx extensions

No response

Extra tools

No response

Additional context

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