Add a shlex pyi (based on upstream)

poezio/poezio_shlex.pyi

+from typing import List, Tuple, Any, TextIO, Union, Optional, Iterable, TypeVar
+import sys
+
+def split(s: str, comments: bool = ..., posix: bool = ...) -> List[str]: ...
+if sys.version_info >= (3, 8):
+    def join(split_command: Iterable[str]) -> str: ...
+def quote(s: str) -> str: ...
+
+_SLT = TypeVar('_SLT', bound=shlex)
+
+class shlex(Iterable[str]):
+    commenters: str
+    wordchars: str
+    whitespace: str
+    escape: str
+    quotes: str
+    escapedquotes: str
+    whitespace_split: bool
+    infile: str
+    instream: TextIO
+    source: str
+    debug: int
+    lineno: int
+    token: str
+    eof: str
+    if sys.version_info >= (3, 6):
+        punctuation_chars: str
+
+    if sys.version_info >= (3, 6):
+        def __init__(self, instream: Union[str, TextIO] = ..., infile: Optional[str] = ...,
+                     posix: bool = ..., punctuation_chars: Union[bool, str] = ...) -> None: ...
+    else:
+        def __init__(self, instream: Union[str, TextIO] = ..., infile: Optional[str] = ...,
+                     posix: bool = ...) -> None: ...
+    def get_token(self) -> Tuple[int, int, str]: ...
+    def push_token(self, tok: str) -> None: ...
+    def read_token(self) -> str: ...
+    def sourcehook(self, filename: str) -> Tuple[str, TextIO]: ...
+    # TODO argument types
+    def push_source(self, newstream: Any, newfile: Any = ...) -> None: ...
+    def pop_source(self) -> None: ...
+    def error_leader(self, infile: str = ...,
+                     lineno: int = ...) -> None: ...
+    def __iter__(self: _SLT) -> _SLT: ...
+    def __next__(self) -> str: ...