Remove whitespace from copy to clipboard component

If there is whitespace in the element containing the value to be copied
then Firefox[1] includes that space in the value it puts in the clipboard.

This is obviously annoying since `foo-bar` might be a valid API key where
`foo-bar ` is not.

This commit fixes that by using the `-` in Jinja to gobble whitespace.

I also looked at doing this in the Javascript, but the browser API for
selecting some text and copying it doesn’t give an obvious place for
using `String.prototype.trim()`.

1. Tested with Firefox 100.0 on Mac OS 12.2.1

app/templates/components/copy-to-clipboard.html

@@ -6,7 +6,7 @@
   {% endif %}
   <div data-module="copy-to-clipboard" data-value="{{ value }}" data-thing="{{ thing }}" data-name="{{ name }}">
     <span class="copy-to-clipboard__value">
-      {% if name|lower != thing|lower %}<span class="govuk-visually-hidden">{{ thing }}: </span>{% endif %}{{ value }}
+      {%- if name|lower != thing|lower %}<span class="govuk-visually-hidden">{{ thing }}: </span>{% endif %}{{ value -}}
     </span>
     <span class="copy-to-clipboard__notice" aria-live="assertive"></span>
   </div>