* Html Reader Not Handling non-ASCII Data Correctly
Fix#2942. Code was changed by #2894 because PHP8.2 will deprecate how it was being done. See linked issue for more details. Dom loadhtml assumes ISO-8859-1 in the absence of a charset attribute or equivalent, and there is no way to override that assumption. Sigh. The suggested replacements are unsuitable in one way or another. I think this will work with minimal disruption (replace ampersand, less than, and greater than with entities representing illegal characters, then use htmlentities, then restore ampersand, less than, and greater than).
* Better Implementation
Use regexp to escape non-ASCII. Less kludgey, less reliant on the vagaries of the PHP maintainers.
* Additional Tests
Test non-ASCII outside of cell contents: sheet title, image alt attribute.
* Apply Same Change in Second Location
Forgot to change loadFromString.
* Additional Test
Confirm escaped ampersand is handled correctly.