Get to feature parity with OG BobaEditor

## General features

- [ ] Characters count
- [ ] Detect empty status
- [ ] Dynamically restrict allowed content (e.g. no embeds, no more than one image)
- [ ] #44

## Inline text attributes

- [x] Bold
- [x] Italic
- [x] Underline
- [x] Strikethrough
- [x] Link
- [x] Spoiler
- [x] Ordered list
- [x] Unordered list
- [x] Code
- [x] Quote
- [x] Heading (1, 2, 3)*
- [x] Clear formatting

**\*Note:** Heading supports nested formatting

## Images

- [x] Add single image block
- [x] Loading placeholder with saved size
- [x] Spoilers

## Gifs

- [ ] Add single gif
- [ ] Gif selector
- [ ] Loading placeholder with saved size
- [ ] Spoilers

## Embeds

### Providers
- [x] Twitter
- [x] Tumblr
- [x] Pixiv
- [ ] Reddit
- [ ] Instagram
- [x] TikTok
- [x] Vimeo
- [x] Bandcamp
- [x] Youtube
- [ ] Generic OEmbed

### General functionality
- [x] Spoilers
- [x] Loading placeholder with saved size

### Per-provider functionality
- [ ] **Twitter:** allow embedding thread