Fix: check `event.defaultPrevented` before handling events to avoid conflicts with other plugins

[RyotaUshio]

Hi, thank you for maintaining this plugin which is important for the community!

As stated in the developer documentation, a community plugin has to check event.defaultPrevented before handling editor-paste and editor-drop events to see if other plugins already handle the event.

• https://docs.obsidian.md/Reference/TypeScript+API/Workspace/on_12
• https://docs.obsidian.md/Reference/TypeScript+API/Workspace/on_13

So I added the two lines according to this. This change will fix conflicts with other plugins such as https://github.com/RyotaUshio/obsidian-advanced-external-links (sorry this is my plugin).

[zolrath]

Makes sense, thanks!