Customized biomes (#396)

* Start with customized biome UI

* Refactor customized page, split logic

* Implement biome replacements

* Remove debug messages

* Disable create button when nothing is modified

src/locales/en.json

@@ -31,7 +31,9 @@
   "copy_share": "Copy share link",
   "copied": "Copied!",
   "copy_context": "Copy context",
+  "customized.error_min_version": "Customized worlds are not available in versions before %0%",
   "customized.basic": "Basic",
+  "customized.biomes": "Biomes",
   "customized.structures": "Structures",
   "customized.ores": "Ores",
   "cutoff": "Cutoff",