Looked into this some more. Ctrl-Break (sending SIGBREAK) terminates programs alright, but doesn't leave room for cleanup or recovery. Curiously, unlike SIGKILL on *nix, it can be handled, but once I install a handler the behavior reverts back to blocking on recv.
I opened [bpo-41437](https://bugs.python.org/issue41437) to see if I can fish out a definitive answer from a core dev.
(Aside: how did I manage to simulate Ctrl-Break? Turns out AHK can send the combo: `F19::send ^{CtrlBreak}`.)
Add TOML.
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Imported from
https://github.com/KDE/syntax-highlighting/blob/2d8eab6f502e7d817b1840ad12463f4562be3999/data/syntax/toml.xml (with trailing whitespaces stripped).
TOML is pretty widely used these days, for instance in the Python ecosystem ([`pyproject.toml`](https://www.python.org/dev/peps/pep-0621/)) and the Rust ecosystem (`Cargo.toml`). It would be nice to support it in Pandoc out of the box.