Add isxidstart and isxidcontinue functions

Author: StanFromIreland

stdlib/unicodedata.pyi

@@ -26,6 +26,10 @@ def digit(chr: str, /) -> int: ...
 @overload
 def digit(chr: str, default: _T, /) -> int | _T: ...
 
+if sys.version_info >= (3, 15):
+    def isxidstart(chr: str, /) -> bool: ...
+    def isxidcontinue(chr: str, /) -> bool: ...
+
 _EastAsianWidth: TypeAlias = Literal["F", "H", "W", "Na", "A", "N"]
 
 def east_asian_width(chr: str, /) -> _EastAsianWidth: ...