Add typos and variants from w3c/silver#248

22 typos + 43 variants = 65 total

The original typos were:

    accessibiltiy
    accessiiblity
    accesssibility
    apporach
    closesly
    congnition
    contrsts
    devleopment
    disabilitiles
    disabiltities
    enduser
    gloassary
    immsersive
    interdependant
    itheir
    meaured
    neads
    organzied
    percentange
    percievable
    protoyping
    techniquest