Support lzma compressed files

Currently lzma compressed files are not supported. They can easily be supported with the same utility as xz (xz-utils), so a change to add support is minor.

will | ~/diffoscope (master): echo a > a
will | ~/diffoscope (master): tar -cf a.tar a
will | ~/diffoscope (master): xz --compress --format=lzma --stdout a.tar > a.tar.lzma
will | ~/diffoscope (master): echo b > a
will | ~/diffoscope (master): tar -cf a.tar a
will | ~/diffoscope (master): xz --compress --format=lzma --stdout a.tar > b.tar.lzma
will | ~/diffoscope (master): diffoscope a.tar.lzma b.tar.lzma
2025-05-23 02:43:43 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
@@ -1,8 +1,8 @@
 00000000: 5d00 0080 00ff ffff ffff ffff ff00 3080  ].............0.
 00000010: 3350 1868 8983 01eb d6c2 f592 2c0c bbe7  3P.h........,...
-00000020: a590 ff73 a121 0d7b 901f eb0b 8e6c 1255  ...s.!.{.....l.U
-00000030: 3a88 2524 8732 a8f4 62d9 f256 c423 8d2d  :.%$.2..b..V.#.-
-00000040: fb3a 5809 606c a5f5 f397 2865 cbd9 924f  .:X.`l....(e...O
-00000050: 0860 9b29 7e16 bce9 92e5 2c1e b62b 4923  .`.)~.....,..+I#
-00000060: 2be0 896a 8413 a4fe 0b32 4ea2 1815 a3c5  +..j.....2N.....
-00000070: 9bd7 7998 ffff d049 c000                 ..y....I..
+00000020: a590 ff73 a121 0d7b 8647 b1d4 24fb 53a5  ...s.!.{.G..$.S.
+00000030: 792b 245f e6f6 43cf 5870 1954 8a0f 0e98  y+$_..C.Xp.T....
+00000040: 395e e470 a854 2c02 83a0 e0bb bddf adfe  9^.p.T,.........
+00000050: 1365 2d28 7da2 e3e6 09de 8cc0 f8a8 d4ca  .e-(}...........
+00000060: 99aa 167e 5948 e190 1083 113e 8bb0 ec10  ...~YH.....>....
+00000070: 1b6f 915e bfff fee4 b400                 .o.^......