[contributor] reorder chapters by task
[contributor] reorder chapters by task

Change-Id: I5b4c5f3d1030651122178aa31a0a005a45373618
Implements: blueprint contributor-guide-reorg

AlekhyaMallina-Vedams/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals,AlekhyaMallina-Vedams/openstack-manuals,openstack/openstack-manuals,openstack/openstack-manuals