Change search "not found" links

[kaleidawave]

This PR adds an additional link to the not found section on the search page in the rustdoc output. This new link points to https://docs.rs/releases/search?q=*input*.

The use case is that I keep going to find an external item when unintentionally on https://doc.rust-lang.org/stable/std/. This provides a quicker way to where I actually want to search docs.rs.

This also shows the current crate name in the section to remind the user what crate is being searched.

---

A concern is that the docs.rs search is by crate name, not by actual items. Maybe the message should be Search crates matching *query*

[rust-log-analyzer]

The job mingw-check-tidy failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

Checking tidy rustdoc_json...
Running eslint on rustdoc JS files

/checkout/src/librustdoc/html/static/js/search.js
  4922:1  error  This line has a length of 105. Maximum allowed is 100  max-len
  4923:1  error  This line has a length of 107. Maximum allowed is 100  max-len

✖ 2 problems (2 errors, 0 warnings)

eslint command failed
`rustdoc-json-types` was not modified.
tidy: Skipping binary file check, read-only filesystem
##[error]tidy error: /checkout/src/librustdoc/html/static/js/search.js:4922: line longer than 100 chars
##[error]tidy error: /checkout/src/librustdoc/html/static/js/search.js:4923: line longer than 100 chars
removing old virtual environment
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'venv'
creating virtual environment at '/checkout/obj/build/venv' using 'python3.10' and 'virtualenv'
Requirement already satisfied: pip in ./build/venv/lib/python3.10/site-packages (25.1.1)
linting python files
All checks passed!
checking python file formatting
28 files already formatted
checking C++ file formatting
some tidy checks failed
Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:01:21
  local time: Sun Jun 22 09:39:11 UTC 2025
  network time: Sun, 22 Jun 2025 09:39:11 GMT
##[error]Process completed with exit code 1.
Post job cleanup.

[lolbinarycat]

Suggested change

	const duckduckgoURL = `https://duckduckgo.com/?q=${encodeURIComponent("rust " + query.userQuery)}`;
	const duckduckgoURL = `https://duckduckgo.com/?q=${encodeURIComponent("rust lang " + query.userQuery)}`;

While we're here we should probably disambiguate so people don't get results about the game (this happens to me sometimes)

[lolbinarycat]

we can apply some simple heuristics to hide this when it would be unhelpful. for example, if query.hasReturnArrow is true, we're doing type-based search, like u8 -> u16, which probably won't give much help.