tectonic 0.15.0 (2024-02-05)

This release contains a grab-bag of nice improvements:

The port of Tectonic’s BibTeX engine to a pure-Rust implementation has been
completed by @CraftSpider (#1077, #1083, #1127, #1129)! It continues
to be the case that this change should be invisible to users, but it shows
that large chunks of Tectonic’s legacy C/C++ code can be migrated to cleaner,
safer, more maintainable Rust over time.
The official Linux builds of Tectonic now link against OpenSSL 3.x, instead of
the old 1.1 series (#1092, @pkgw). This should improve binary
compatibility on mainstream platforms. If you need a build that uses the older
series, you’ll have to compile it yourself.
The --web-bundle flag can now be used in more situations, specifically
tectonic -X new and tectonic -X init (#1132, @bryango).
As part of the above work, you can now activate the "V2" interface with the
-X flag in more places on the Tectonic command line.
The Tectonic.toml file used by the "V2" interface now supports a
[metadata] section for arbitrary structured user metadata (#1120,
@rm-dr). This is useful for custom tools that build on top of Tectonic,
where you might want to have some custom pieces of information about each
document in a group.
The "V2" interface also now supports external commands (#1103, @rm-dr). If
you have a program named tectonic-blah in your search path, running
tectonic -X blah will execute it.
Running tectonic -Z help (as opposed to tectonic -Zhelp) now actually
works (#1064, #1084, @pkgw).

Build changes:

You can now cross-compile Tectonic to the aarch64-unknown-linux-musl target
(#1089, @pkgw).
MIPS is no longer supported as a build target (#1076, @CraftSpider). It
dropped to Tier 3 support by the Rust language, which makes it difficult to
support in our continuous integration systems. Sorry, MIPS!

Documentation fixes:

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