🖼️ Add fancy centered icon as a `.png` file

🔀 Merge #463: 🔖 v1.8.0

✨ Create CONTRIBUTING.md

🔀 Merge #459: 🔖 v1.8.0-beta.4

🔀 Merge #458: 🔖 v1.8.0-beta.3

### Fixes

- Fixed On-Summon Functions and On-Apply Functions not functioning.

🔀 Merge #457: 🔖 v1.8.0-beta.2

### Changes

- ⚠️ **BREAKING** — Removed `custom_name`, `custom_name_visible`,
`useNbt`, and `nbt` from Display Entity Configs. Use the new 'On Summon
Function' and 'On Apply Function' settings to configure entity NBT
instead.
- ⚠️ **BREAKING** — Removed `inherit_settings` from Display Entity
Configs. It didn't work properly and was causing more issues than it
solved. Use the new copy / paste config actions instead.
- Replaced unique node configs with universal DisplayEntityConfig.
- Added 'Copy Display Entity Config' and 'Paste Display Entity Config'
actions to context menus for Groups, Text Displays, Item Displays, and
Block Displays.
- Added 'On Summon Function' to Display Entity Configs.
- Added 'On Apply Function' to Per-variant Display Entity Configs.
- Improved undo / redo history and behavior for TextDisplays,
ItemDisplays, and BlockDisplays.
- Improved the Render Box preview's reactivity.

### Fixes

- Fixed rotation validation not checking the correct version, and
marking any rotation as invalid.
- Fixed Blueprints becoming unsavable after opening.
- Fixed Blueprints becoming unsavable after converting from another
format.
- Fixed annoying element panel UI flicker when selecting or transforming
TextDisplays, ItemDisplays, or BlockDisplays.
- Fixed uncaught error when deleting a text display.
- Fixed outdated warning not appearing until the second reload after
rig_hash was modified.
- Fixed custom outliner elements inheriting the same properties list,
and therefor causing every node which inherits it to include every other
node's properties in it's saved data.

🔀 Merge #456: 🔖 v1.8.0-beta.1

### Related issues not mentioned in commits
- Fixes #455 
- Fixes #453 
- Fixes #450
- Fixes #448 
- Fixes #445 
- Fixes #441 
- Fixes #438

🔀 Merge v1.7.2 (#418)

🔀 Merge next into main: v1.7.1 (#416)

🔀 Merge #411: 🔖 Release v1.7.0