Add page listing "missing languages"

[xrotwang]

This list could be generated by comparison with Glottolog, also adding information about references of suitable doctypes.

[xrotwang]

See ASJP's contribute page for an example.

[drammock]

👍

[bambooforest]

+1 ... the list will be long, but very helpful also for identifying through Glottolog linguistic descriptions to add the remaining missing inventories.