Added hintText option to add link text

[Bayramito]

This PR adds small feature to be able to change the text in the EditLinkBar via theme props.

Example usage

  const editor = useEditorBridge({
    theme: {
      toolbar: {
        linkBarTheme: {
          hintText: "Apply", // Changes from Insert to Apply
        },
      },
    },
  });

[17Amir17]

Wondering if this should be part of EditorTheme or a prop on the toolbar cc @GuySerfaty