Add keyboard special key support for web content interaction

Enter, Backspace, Tab, Escape, Delete, arrow keys, Home, End,
PageUp, PageDown now forward to Servo. Previously only printable
characters reached the web engine, making forms unusable.

crates/ely_servo_host/src/keyboard.rs

@@ -1,6 +1,25 @@
-use servo::Code;
+use servo::{Code, Key};
 
-pub(crate) fn keyboard_code_for_character(character: char) -> Code {
+pub(crate) fn key_and_code_for_character(character: char) -> (Key, Code) {
+    match character {
+        '\n' | '\r' => (Key::Enter, Code::Enter),
+        '\x08' => (Key::Backspace, Code::Backspace),
+        '\t' => (Key::Tab, Code::Tab),
+        '\x1b' => (Key::Escape, Code::Escape),
+        '\x7f' => (Key::Delete, Code::Delete),
+        '\u{F700}' => (Key::ArrowUp, Code::ArrowUp),
+        '\u{F701}' => (Key::ArrowDown, Code::ArrowDown),
+        '\u{F702}' => (Key::ArrowLeft, Code::ArrowLeft),
+        '\u{F703}' => (Key::ArrowRight, Code::ArrowRight),
+        '\u{F729}' => (Key::Home, Code::Home),
+        '\u{F72B}' => (Key::End, Code::End),
+        '\u{F72C}' => (Key::PageUp, Code::PageUp),
+        '\u{F72D}' => (Key::PageDown, Code::PageDown),
+        _ => (Key::Character(character.to_string()), printable_code(character)),
+    }
+}
+
+fn printable_code(character: char) -> Code {
     match character {
         'a' | 'A' => Code::KeyA,
         'b' | 'B' => Code::KeyB,