OSS-Fuzz: Add new fuzzer upstream

[arthurscchan]

I’ve noticed that this project is already included in OSS-Fuzz for fuzzing (https://github.com/google/oss-fuzz/tree/39036e0ed94fefa958d7c9a20a69619c832b682a/projects/unicode-rs), although the current code coverage appears to be limited. This PR proposes adding a new fuzzer that targets specific functions for Unicode string processing, with the goal of expanding the fuzzing scope and improving code exploration. I’d be grateful for any feedback or suggested changes. Thank you.

[Manishearth]

Needs formatting

[arthurscchan]

Thanks. I have fixed the formatting. Sorry for missing the CI result.

[Manishearth]

 --> fuzz_targets/process.rs:1:1
  |
1 | -// The fuzzing harness fuzz test some of the the
  | ^ expected item
  |
  = note: for a full list of items that can appear in modules, see <https://doc.rust-lang.org/reference/items.html>

[Manishearth]

Needs formatting.

[arthurscchan]

Sorry for the type and formatting, have fixed that.