Feature: Migrate post from the old website

[syphax-bouazzouni]

Context

This PR migrates the old posts from the old website to the new one as blog posts.
Below are listed the migrated posts:

	Title	Release date	Category	Author
✅	https://ontoportal.org/ontoportal-virtual-appliance-release-3-0-is-here/	Aug 13, 2020	About the Appliance, Appliance, Happenings, News	John graybeal
✅	https://ontoportal.org/allegrograph-inside/	Jun 13, 2020	About the Appliance, Happenings, News	John graybeal
✅	https://ontoportal.org/ontoportal-virtual-appliance-rev-3-coming-soon/	Jun 6, 2020	About the Appliance, Appliance, Happenings, News	John graybeal
✅	https://ontoportal.org/the-new-ontoportal-alliance/	Feb 5, 2020	Alliance History	John graybeal
✅	https://ontoportal.org/ontoportal-alliance-at-rda-plenary-14/	Feb 5, 2020	Alliance History	John graybeal
✅	https://ontoportal.org/ontoportal-alliance-at-rda-plenary-13/	Apr 4, 2019	Alliance History	John graybeal
✅	https://ontoportal.org/about-the-ontoportal-alliance-background/	Apr 2, 2019	Alliance, Alliance History	John graybeal
✅	https://ontoportal.org/	Feb 4, 2020	About the Alliance, Alliance	John graybeal