feat(checkbox): Add keyboard handling for Enter and Space keys to tog… (

#946)

### Summary of Changes
- Added keyboard functionality to the input component to toggle the
checked state when the Enter or Space key is pressed.
### Changes Made
1. Implemented the handleKeyDown function:
```
private handleKeyDown(event: KeyboardEvent) {
    if (event.code === "Enter" || event.code === "Space") {
        this.checked = !this.checked;
        this.onChange(this.checked);
        event.preventDefault();
    }
}

```
2. Associated the function with the @keydown event listener:
`<input @keydown=${this.handleKeyDown} />`

### Reason for Changes
This change was made to enhance user interaction with form elements via
the keyboard and to improve accessibility.

---------

Co-authored-by: Buse Selvi <[email protected]>
Co-authored-by: Erbil <[email protected]>

src/components/checkbox-group/checkbox/bl-checkbox.ts

@@ -177,6 +177,13 @@ export default class BlCheckbox extends FormControlMixin(LitElement) {
   private handleFieldValueChange = (event: CustomEvent<Array<string>>) => {
     this.checked = event.detail.includes(this.value);
   };
+  private handleKeyDown(event: KeyboardEvent) {
+    if (event.code === "Space") {
+      this.checked = !this.checked;
+      this.onChange(this.checked);
+      event.preventDefault();
+    }
+  }
 
   render(): TemplateResult {
     let icon = "";
@@ -206,6 +213,7 @@ export default class BlCheckbox extends FormControlMixin(LitElement) {
           aria-readonly=${this.disabled}
           .indeterminate=${this.indeterminate}
           @change=${this.handleChange}
+          @keydown=${this.handleKeyDown}
           value=${ifDefined(this.value)}
           @blur=${this.blur}
         />