Add release notes for slim sidebar
Add release notes for slim sidebar

mixxorz/wagtail,jnns/wagtail,rsalmaso/wagtail,thenewguy/wagtail,rsalmaso/wagtail,zerolab/wagtail,jnns/wagtail,wagtail/wagtail,mixxorz/wagtail,thenewguy/wagtail,jnns/wagtail,wagtail/wagtail,jnns/wagtail,wagtail/wagtail,rsalmaso/wagtail,wagtail/wagtail,rsalmaso/wagtail,thenewguy/wagtail,zerolab/wagtail,thenewguy/wagtail,rsalmaso/wagtail,wagtail/wagtail,zerolab/wagtail,mixxorz/wagtail,thenewguy/wagtail,mixxorz/wagtail,zerolab/wagtail,mixxorz/wagtail,zerolab/wagtail