Can `remain` support checking if the constant names in a module are sorted?

Hi,

First of all, thank you for this nice package. I have just discovered it and have started using it in my project.

I have another use case related to constants declared in a module, not sure if `remain` can support it.
For example, the following module is used to organize keywords, which are string constants:

```rust
/// Keyword to parse command line arguments
pub mod kw {
pub const CLANG_OPTIONS: &str = "clang-options";
pub const DEBUG_MODE: &str = "debug-mode";
pub const DISABLE_NORMALIZE: &str = "disable-normalize";
pub const DISABLE_OPTIMIZE: &str = "disable-optimize";
pub const DISABLE_PRINTING: &str = "disable-printing";
pub const INSTRUMENT_BUG_ANNOTS: &str = "instrument-bug-annots";
pub const PRINT_COMPILED_PROG: &str = "print-compiled-prog";
pub const PRINT_OPTIMIZED_PROG: &str = "print-optimized-prog";
pub const PRINT_NORMALIZED_PROG: &str = "print-normalized-prog";
pub const RUSTC_OPTIONS: &str = "rustc-options";
pub const SOLANG_OPTIONS: &str = "solang-options";
pub const SOLC_OPTIONS: &str = "solc-options";
pub const COMPILER: &str = "compiler";
}
```

The list may get longer. So, I wonder if `remain` can support checking if all constant names are sorted?

It will be very useful to avoid the duplication of constants.