+ new script telex2vni
Support two special accent-cancel forms

In Telex, the duplication of modifier is used to cancel the
accents/hats. For example, "aaa" and "aww" will print "aa"
and "aw" (resp.). In VNI, they are "a66" and "a88".

The 3rd form of cancel form is sth like "ass" (telex) which
can be tranformed natually into VNI code "a11" (vni)
Using :telex2vni to generate VNI table
Update README: we now have only one table Telex.txt.in
Remove the table VNI bc it can be generated from Telex