docs: Restructure Main Page

    * Restructure main page

    * Supported-technologies folder moved one level up

    * This is part of MR: https://booting.oniroproject.org/distro/docs/-/merge_requests/227

    * Rework on the documentation flow

    * Closes:  https://git.ostc-eu.org/distro/docs/-/issues/80



Signed-off-by: Gururaj Shetty <gururaj.shetty@huawei.com>