Reminder display improvement in markdown editor

[uphy]

TODO

• [x] PillWidget to svelte component
• [x] Replace css injection
• [x] Performance improvement (Avoid re-reading the entire document on every update. Currently, the whole text is re-parsed each time the caret moves or content changes)
• [ ] Add setting to disable this extension
• [ ] window.setInterval() to Obsidian's one
• [ ] Simplify showDateTimeChooserModal() arguments (maybe we can omit step)
• [ ] Documents