Make extensions case insensitive on linux

src/filepicker.rs

@@ -1,4 +1,5 @@
 use std::{
+    fmt::Write as _,
     path::PathBuf,
     sync::{Arc, Weak},
 };
@@ -49,6 +50,23 @@ pub struct FileDialogBuilder {
 
 impl FileDialogBuilder {
     pub fn add_filter(self, name: impl Into<String>, extensions: &[impl ToString]) -> Self {
+        #[cfg(target_os = "linux")]
+        let exts = extensions
+            .iter()
+            .map(|ext| {
+                let mut normalized = String::new();
+                for char in ext.to_string().chars() {
+                    if char.is_ascii_lowercase() {
+                        let _ = write!(&mut normalized, "[{char}{}]", char.to_ascii_uppercase());
+                    } else {
+                        normalized.push(char);
+                    }
+                }
+                normalized
+            })
+            .collect::<Vec<_>>();
+        #[cfg(target_os = "linux")]
+        let extensions = &exts;
         Self {
             dialog: self.dialog.add_filter(name, extensions),
             ..self