wl-clipboard 2.1

2.1 is a minor release with a few bugfixes and fish completions.

• Fixed wl-copy hangs when followed by a pipe (e.g. echo "text to copy" | wl-copy | cat) by properly closing stdin/stdout file descriptors.
• Fixed a crash that occasionally happened in do_set_selection().
• Added fish completions. Similarly to zsh completions, a fishcompletiondir meson flag has been added to control them at build time.
• Fixed a build warning related to pointer arithmetic.