Image support via new attachments feature

[simonw]

See LLM 0.17a0:

• Solve multi-modal models with a new concept of "attachments" llm#587

[simonw]

For the test:

TINY_PNG = (
    b"\x89PNG\r\n\x1a\n\x00\x00\x00\rIHDR\x00\x00\x00\xa6\x00\x00\x01\x1a"
    b"\x02\x03\x00\x00\x00\xe6\x99\xc4^\x00\x00\x00\tPLTE\xff\xff\xff"
    b"\x00\xff\x00\xfe\x01\x00\x12t\x01J\x00\x00\x00GIDATx\xda\xed\xd81\x11"
    b"\x000\x08\xc0\xc0.]\xea\xaf&Q\x89\x04V\xe0>\xf3+\xc8\x91Z\xf4\xa2\x08EQ\x14E"
    b"Q\x14EQ\x14EQ\xd4B\x91$I3\xbb\xbf\x08EQ\x14EQ\x14EQ\x14E\xd1\xa5"
    b"\xd4\x17\x91\xc6\x95\x05\x15\x0f\x9f\xc5\t\x9f\xa4\x00\x00\x00\x00IEND\xaeB`"
    b"\x82"
)

Created that using this pattern: https://til.simonwillison.net/python/inlining-binary-data

From: