Suggest correct path in include_bytes!
`include_bytes!` paths are relative, and I'm often not sure how nested is the `.rs` file that I'm editing, so I have to guess the number of `"../.."`. This change searches `..` and `../..` for the given file and offers corrected path as a suggestion.
I wasn't sure how to get the right span, and how to properly escape it.
```text
error: couldn't read src/file.txt: No such file or directory (os error 2)
--> src/main.rs:2:13
|
2 | let x = include_bytes!("file.txt");
| ^^^^^^^^^^^^^^^----------^
| |
| help: it's in a parent directory: `"../../file.txt"`
```
463a11bef4