Accept a byte-order mark in reskate-levels.json

The launcher and the server already skip one, so a map saved with a BOM was
listed everywhere but left out in game.

Engine/Game/World/custom_level_manifest.cpp

@@ -86,9 +86,9 @@ void exact_fields(const Json& object, std::initializer_list<std::string_view> ex
 CustomLevelManifest parse(std::string_view text) {
     if (text.size() > custom_level_manifest_max_bytes)
         throw std::runtime_error("custom-level manifest exceeds 64 KiB");
-    if (text.starts_with("\xef\xbb\xbf"))
-        throw std::runtime_error("custom-level manifest must not contain a UTF-8 BOM");
 
+    // Json::parse skips a byte-order mark, which several Windows editors still
+    // write. The launcher and the server accept one, so the game must too.
     const auto root = Json::parse(text, JsonLimits{
         custom_level_manifest_max_bytes, 8, 8192});
     exact_fields(root, {"schema", "levels"}, "custom-level manifest");

Engine/Game/World/custom_level_manifest.h

@@ -23,7 +23,7 @@ struct CustomLevelManifest {
     std::string issue;
 };
 
-// Parse the Studio-authored Patch/dingosdk-levels.json contract. Invalid input
+// Parse a mod's or the Patch folder's reskate-levels.json. Invalid input
 // fails closed: no partial set of destinations is returned.
 CustomLevelManifest parse_custom_level_manifest(std::string_view text) noexcept;
 CustomLevelManifest read_custom_level_manifest(const std::filesystem::path& path) noexcept;