Search CustomIndexer workflow using IndexProperty doesn't work if property name is not lowercase

More context on this bug: https://unity.slack.com/archives/CGL2NFY0N/p1742826397189369

Object.Indexer.IndexProperty doesn't lowercase the property name. Which means if a user registers a property not fully lower case, the user won't be able to find it.

• IndexProperty<PropertyType, PropertyOwnerType> : should have a version with saveKeyword and exact at false
• We should have a manual section to explain how to do CustomIndexing
• This blog post should be updated on all these gotchas: https://github.com/Unity-Technologies/com.unity.search.extensions/wiki/Custom-Asset-Indexing
• We should have a template script to create a CustomIndexer with a valid example.