Add new functions to api in docs

Author: david-pl

docs/src/api.md

@@ -438,6 +438,10 @@ tracedistance_nh
 entropy_vn
 ```
 
+```@docs
+entropy_renyi
+```
+
 ```@docs
 fidelity
 ```
@@ -458,6 +462,14 @@ negativity
 logarithmic_negativity
 ```
 
+```@docs
+entanglement_entropy
+```
+
+```@docs
+avg_gate_fidelity
+```
+
 ## [State definitions](@id API: State definitions)
 
 ```@docs