* Allow setting an additional alpha on a border
See #1863.
* Update the ChangeLog
* Add snapshot tests for the border alpha value
* Extend the border snapshot tests
While this doesn't test *every* permutation, it covers enough bases that if
something were to change it should catch it.
* Tweak a typo in the border style examples
* Add border transparency percentage to the border docs
* Add a CSS example for using border transparency
* Add Color.multiply_alpha
* Update the CHANGELOG
* Multiply the alpha on a colour rather than replace it
As requested in
https://github.com/Textualize/textual/pull/1954#pullrequestreview-1328170386
(actually required while talking in person with Will, but noted in the
above)
* Multiply the alpha on a border colour rather than replace it
As requested in
https://github.com/Textualize/textual/pull/1954#pullrequestreview-1328170386
(actually requested while talking in person with Will, but noted in the
above)
