Release Newsboat 2.39

Added
=====

- New `bind` command, which is an improvement on both `bind-key` and `macro`.
    It allows multi-key bindings (that's new!) which execute one or more actions
    (similar to macros), and can have a description that'll be displayed in the
    help dialog (that's new too!). It also offers an additional syntax for
    specifying keys: instead of `^R`, one can write `<C-r>`. Multi-key bindings
    are slightly limited in that bindings with same prefix must all be the same
    length to avoid ambiguity when executing them (if I had bindings `for` and
    `fork`, and typed `for`, Newsboat wouldn't know if that's it or I'm going to
    type `k` next) (newsboat#1165) (Dennis van der Schagt, Alexander Batischev, Lysander
    Trischler)
- contrib/newsboat-idlefeeds.sh: a script to show feeds that weren't updated in
    a given amount of time (T3SQ8)

Changed
=======

- Highlighting in the help form is now case-insensitive (newsboat#2998) (Juho Eerola)
- Updated translations: Dutch (Dennis van der Schagt),
    German (Lysander Trischler), Italian (Mauro Scomparin), Polish (Carno),
    Russian and Ukrainian (Alexander Batischev), Swedish (Dennis Öberg),
    Turkish (Emir SARI)
- Bumped minimum supported Rust version to 1.81.0

Deprecated
==========

- Compilers that don't support C++17. This release compiles with `-std=c++17`,
    but only for compatibility with header files of libicu 75+; Newsboat itself
    only uses C++14 for now. The next release might start using C++17 features,
    so please open an issue if that'll cause problems for you (newsboat#3031) (Alexander
    Batischev)

Removed
=======

- Support for Clang 4, because it doesn't accept `-std=c++17` (newsboat#3031) (Alexander
    Batischev)

Fixed
=====

- Crash when setting a non-existent variable (newsboat#2989) (Dennis van der Schagt)
- Highlights not displayed for searches that contain less-than sign, due to
    errors in quoting (newsboat#3008) (Juho Eerola)
- Building with libicu 75+, which requires C++17. libicu is an indirect
    dependency of Newsboat via libxml2 (newsboat#3031) (Alexander Batischev)