v4.28.0

MixedModels v4.28.0

NEWS file.
Diff since v4.27.1

NB: Closed issues and pull requests are sorted temporally and so may
include backports to other versions or work in the development branch for
an upcoming breaking release. Please see the NEWS file
for changes sorted by release.
Closed issues:

• Non-positive definite matrix when fitting nested GLMM (#792)

Merged pull requests:

• attempt to find better starting values for GLMM when defaults aren't positive semidefinite (#796) (@palday)