update the changelog

CHANGELOG.md

@@ -4,6 +4,11 @@ All notable changes to this project will be documented in this file.
 ## [Unreleased]
 
 ### Added
+- New analytic beam classes: AiryBeam, GaussianBeam, ShortDipoleBeam, UniformBeam
+that support evaluating either the efield or power beam in any direction and frequency.
+- A new BeamInterface class that provides a unified interface to UVBeam and analytic
+beam objects to get beam responses in any direction and frequency (via
+interpolation or evaluation as appropriate).
 - A new `freq_interp_kind` parameter to `UVBeam.interp`, `UVBeam._interp_az_za_rect_spline`
 and `UVBeam._interp_healpix_bilinear` to allow the frequency interpolation
 specification to be passed into the methods. Note this defaults to "cubic" rather