PDF dictionary key must be a name

[radarhere]

Rather than allowing any type of value for a dictionary key

Pillow/src/PIL/PdfParser.py

Lines 881 to 891 in 8bbb9ec

	m = cls.re_dict_start.match(data, offset)
	if m:
	offset = m.end()
	result: dict[Any, Any] = {}
	m = cls.re_dict_end.match(data, offset)
	current_offset: int | None = offset
	while not m:
	assert current_offset is not None
	key, current_offset = cls.get_value(
	data, current_offset, max_nesting=max_nesting - 1
	)

this PR restricts the key to a name.

https://web.archive.org/web/20211126185945/https://www.adobe.com/content/dam/acom/en/devnet/pdf/pdfs/pdf_reference_archives/PDFReference.pdf

A dictionary object is an associative table containing pairs of objects, known as the dictionary's entries. The first element of each entry is the key and the second element is the value. The key must be a name