feat: support online search and related settings

[notSagyo]

Description

Adds support for online search, works without Surfing but integrates seemingly with it. This should address and resolve #1.

I've seen some commits addressing this, but they didn't seem to be implemented yet. This should fix it in the meantime, and also adds functionality even without Surfing.

Features

• Pressing Alt+Enter always performs an online search
• Pressing Mod+Alt+Enter does the same in a new tab
• Setting: search online instead of creating file when the input isn't an existing file
• Setting: change default search engine
• Changes the icon and text to indicate that an online search will be performed instead of creating a file

Notes

I tried combining different settings to ensure everything works properly. I haven't worked with Svelte or Obsidian's API previously, so this may not follow best practices but I tried to achieve consistency with existing code.

Potential improvements include using a dropdown to select search engines instead of writing the URL, and showing search results in the current tab instead of opening a new one and closing the previous.

[olrenso]

Hi, thank you for the PR. I'll look into it as soon as I have some free time and let you know.