Add lzma comparator (#409)
Behavior using example from #409 (closed) after this patch:
will | ~/diffoscope (lzma-comparator): diffoscope a.tar.lzma b.tar.lzma
2025-05-23 02:41:52 W: diffoscope.comparators.xml: Vulnerable version of pyexpat detected; disabling comparison of XML documents. Install defusedxml or upgrade your pyexpat.
--- a.tar.lzma
+++ b.tar.lzma
│ --- a.tar
├── +++ b.tar
│ ├── file list
│ │ @@ -1 +1 @@
│ │ --rw-r--r-- 0 will (1000) will (1000) 2 2025-05-23 02:40:41.000000 a
│ │ +-rw-r--r-- 0 will (1000) will (1000) 2 2025-05-23 02:41:25.000000 a
│ ├── a
│ │ @@ -1 +1 @@
│ │ -a
│ │ +b