Add NeedletailError to stub file

[audy]

Adds NeedletailError to the type stub file so static analyzers can find it:

# asdf.py
import needletail

raise needletail.NeedletailError

before

$ty check asdf.py
WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
error[unresolved-attribute]: Type `<module 'needletail'>` has no attribute `NeedletailError`
 --> asdf.py:4:7
  |
2 | import needletail
3 |
4 | raise needletail.NeedletailError
  |       ^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
info: rule `unresolved-attribute` is enabled by default

after

ty check asdf.py
WARN ty is pre-release software and not ready for production use. Expect to encounter bugs, missing features, and fatal errors.
All checks passed!