add --mime-type(-m) to ls in the type column (#7616)

# Description

This PR adds the `mime-type` to the `type` column if you add the
`--mime-type(-m)` flag to `ls`.
<img width="853" alt="Screenshot 2022-12-27 at 11 43 20 AM"
src="https://user-images.githubusercontent.com/343840/209705499-27fe40fe-0356-4d9d-97f2-4b2dc52e0963.png">

<img width="781" alt="Screenshot 2022-12-27 at 11 45 53 AM"
src="https://user-images.githubusercontent.com/343840/209705509-4d677389-fd68-401e-a7af-3fc6052743b6.png">

# User-Facing Changes

If you specify the `-m` flag, you get the "guessed at" mime type. The
guess is based on the file name and uses this crate
https://docs.rs/mime_guess/latest/mime_guess/ for the guessing.

Part of issue #7612 and and #7524

There's some debate on if the `mime-type` should be added to the `type`
column or if there should be a separate `mime` column. I tend to lean on
the side of `type` since it's technically a type and it's only in that
column if you ask it to be there. Also, I'd prefer to reuse a column
rather than having a list of sprawling columns. Also, as @KodiCraft
suggested, there is precedence as with `ls -d` where the summed size is
in the size column.

I could go either way and if someone wants to create a `mime` column,
we'd probably accept it.

# Tests + Formatting

Don't forget to add tests that cover your changes.

Make sure you've run and fixed any issues with these commands:

- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass

# After Submitting

If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.

crates/nu-command/src/filesystem/ls.rs

@@ -62,6 +62,7 @@ impl Command for Ls {
                 "List the specified directory itself instead of its contents",
                 Some('D'),
             )
+            .switch("mime-type", "Show mime-type in type column", Some('m'))
             .category(Category::FileSystem)
     }
 
@@ -78,6 +79,7 @@ impl Command for Ls {
         let full_paths = call.has_flag("full-paths");
         let du = call.has_flag("du");
         let directory = call.has_flag("directory");
+        let use_mime_type = call.has_flag("mime-type");
         let ctrl_c = engine_state.ctrlc.clone();
         let call_span = call.head;
         let cwd = current_dir(engine_state, stack)?;
@@ -250,6 +252,7 @@ impl Command for Ls {
                                 long,
                                 du,
                                 ctrl_c.clone(),
+                                use_mime_type,
                             );
                             match entry {
                                 Ok(value) => Some(value),
@@ -365,7 +368,7 @@ use std::os::unix::fs::FileTypeExt;
 use std::path::Path;
 use std::sync::atomic::AtomicBool;
 
-pub fn get_file_type(md: &std::fs::Metadata) -> &str {
+pub fn get_file_type(md: &std::fs::Metadata, display_name: &str, use_mime_type: bool) -> String {
     let ft = md.file_type();
     let mut file_type = "unknown";
     if ft.is_dir() {
@@ -388,18 +391,32 @@ pub fn get_file_type(md: &std::fs::Metadata) -> &str {
             }
         }
     }
-    file_type
+    if use_mime_type {
+        let guess = mime_guess::from_path(display_name);
+        let mime_guess = match guess.first() {
+            Some(mime_type) => mime_type.essence_str().to_string(),
+            None => "unknown".to_string(),
+        };
+        if file_type == "file" {
+            mime_guess
+        } else {
+            file_type.to_string()
+        }
+    } else {
+        file_type.to_string()
+    }
 }
 
 #[allow(clippy::too_many_arguments)]
 pub(crate) fn dir_entry_dict(
     filename: &std::path::Path, // absolute path
-    display_name: &str,         // gile name to be displayed
+    display_name: &str,         // file name to be displayed
     metadata: Option<&std::fs::Metadata>,
     span: Span,
     long: bool,
     du: bool,
     ctrl_c: Option<Arc<AtomicBool>>,
+    use_mime_type: bool,
 ) -> Result<Value, ShellError> {
     #[cfg(windows)]
     if metadata.is_none() {
@@ -408,7 +425,7 @@ pub(crate) fn dir_entry_dict(
 
     let mut cols = vec![];
     let mut vals = vec![];
-    let mut file_type = "unknown";
+    let mut file_type = "unknown".to_string();
 
     cols.push("name".into());
     vals.push(Value::String {
@@ -417,10 +434,10 @@ pub(crate) fn dir_entry_dict(
     });
 
     if let Some(md) = metadata {
-        file_type = get_file_type(md);
+        file_type = get_file_type(md, display_name, use_mime_type);
         cols.push("type".into());
         vals.push(Value::String {
-            val: file_type.to_string(),
+            val: file_type.clone(),
             span,
         });
     } else {