Include reference to initialize properties

[jwrosewell]

documentation/src/devicedetection/features/performanceoptions.md

Line 12 in f9f9096

# Performance profile templates

The 4.5 launch blog referenced fast property retrieval but the page on performance doesn't mention it.

https://51degrees.com/blog/version-45-launch#faster-property-retrieval

Amend the page to include details of property indexing and then link to the page from the blog.