update types

pass headerHeight

make the array match defensive

update changelog

Merge pull request #85 from mckervinc/feature/frozen

add ability to freeze columns

Merge pull request #84 from mckervinc/feature/resize-observer

v0.5.0 - handle resize in a modern fashion

Merge pull request #82 from mckervinc/feature/heights

Feature: Add footer prop to columns array

Merge pull request #81 from mckervinc/feature/footer

update footer props

add footer

site tweaks