added jsonsubtypes as plain folder

Assets/Plugins/JsonSubTypes/.editorconfig

Assets/Plugins/JsonSubTypes/.gitignore

Assets/Plugins/JsonSubTypes/CHANGELOG.md

Assets/Plugins/JsonSubTypes/CHANGELOG.md.meta

Assets/Plugins/JsonSubTypes/CODE_OF_CONDUCT.md

Assets/Plugins/JsonSubTypes/CODE_OF_CONDUCT.md.meta

Assets/Plugins/JsonSubTypes/JsonSubTypes.meta

Assets/Plugins/JsonSubTypes/JsonSubTypes.sln.meta

...ts/Plugins/JsonSubTypes/JsonSubTypes/JsonSubTypes.Key.snk

...ugins/JsonSubTypes/JsonSubTypes/JsonSubTypes.Key.snk.meta

...lugins/JsonSubTypes/JsonSubTypes/JsonSubTypes.csproj.meta

Assets/Plugins/JsonSubTypes/JsonSubTypes/JsonSubtypes.cs

...ts/Plugins/JsonSubTypes/JsonSubTypes/JsonSubtypes.cs.meta

...JsonSubTypes/JsonSubtypesByDiscriminatorValueConverter.cs

...ubTypes/JsonSubtypesByDiscriminatorValueConverter.cs.meta

...s/JsonSubTypes/JsonSubtypesByPropertyPresenceConverter.cs

...nSubTypes/JsonSubtypesByPropertyPresenceConverter.cs.meta

...lugins/JsonSubTypes/JsonSubTypes/JsonSubtypesConverter.cs

...s/JsonSubTypes/JsonSubTypes/JsonSubtypesConverter.cs.meta

...JsonSubTypes/JsonSubTypes/JsonSubtypesConverterBuilder.cs