clipboard: Always copy as plain text in Wayland #9737

`wl-copy` by default tries to determine the mime type of a copied bit of
text. From the [readme](https://github.com/bugaevc/wl-clipboard):

> wl-copy automatically infers the type of the copied content by running
> xdg-mime(1) on it.

So copying a Ruby script from Nvim may store it in the Wayland clipboard
as mime-type `application/x-ruby`.

This is a small reproduction without Nvim:

    $ cat test.rb
    #!/usr/bin/env ruby
    puts 'hello world'
    $ cat test.rb | wl-copy
    $ wl-paste --list-types
    application/x-ruby

This commit fixes that by telling wl-copy that all text copied from
Nvim has the mime type `text/plain`.

    $ cat test.rb | wl-copy --type text/plain
    $ wl-paste --list-types
    text/plain;charset=utf-8

0 files changed, 0 insertions, 0 deletions