Describe the bug
+.nan and -.nan are parsed as .nan

To Reproduce

+.nan: +.nan 
+.nan: +.nan
-.NaN: -.NaN
-.NaN: -.NaN
.NAN: .NAN
.NAN: .NAN

(Github correctly ignores [+-].nan, but also seems to interpret - as seq)

Expected behaviour
[+-].nan should be parsed as type str

tag-resolution

• Environment: VSCode 1.89
• yaml: 2.4.2

Additional context
also no error is given when multiple keys are given with the same value of type .nan