Support f32 and f64 in decay functions

[alpoi-x]

Looks like f32 and f64 were missed from the Function macro defined here

This pr adds the missing float types to the list and adds a test to ensure it is serialised correctly

docs: function score query supports all numeric field types

[alpoi-x]

Any chance of a release? 😅

[buinauskas]

@alpoi-x a pretty big chance of release, I've had a rough start of the year, sorry 😅