Rename ws to websocket and clean up API

README.md

accept.go

datatype.go

datatype_string.go

dial.go

doc.go

example_test.go

go.mod

go.sum

header.go

json.go

mask.go

opcode.go

opcode_string.go

statuscode.go

statuscode_string.go

websocket.go

wsjson/wsjon.go

wspb/wspb.go