Schematic, Litematica, Structure Block!

This was actually really simple! Turns out these are just plain NBT anyways, so I just had to add some additional tests into NBTify to ensure things were reading and writing symmetrically when working with these file types.

https://fileinfo.com/extension/schematic (didn't know there were two different extension types! Glad I double-checked this)
https://fileinfo.com/extension/schem
https://github.com/puregero/SchemToSchematic/ (yoooo!!! Going to have to look into helping to contribute to this project :D)

index.html

@@ -22,7 +22,7 @@
 <header>
  <img draggable="false" src="./icon.svg" alt="">
  <button onclick="fileOpener.click();">Open</button>
- <input id="fileOpener" type="file" accept="application/octet-stream, .nbt, .dat, .dat_old">
+ <input id="fileOpener" type="file" accept="application/octet-stream, .nbt, .dat, .dat_old, .mcstructure, .litematic, .schem, .schematic">
  <button id="saver" disabled>Save</button>
  <button id="formatOpener" disabled>Format Options...</button>
  <label style="margin-inline-start: auto;">

public/manifest.webmanifest

@@ -29,7 +29,7 @@
  {
  "action": "./",
  "accept": {
- "application/octet-stream": [".nbt", ".dat", ".dat_old"]
+ "application/octet-stream": [".nbt", ".dat", ".dat_old", ".mcstructure", ".litematic", ".schem", ".schematic"]
  }
  }
  ]