Add 'alt-bg' color for striped lines (#4370)

Test cases:

1. 'jump' should show alternating background colors even when 'alt-bg' is
not defined as before.

  go run main.go --bind load:jump

Two differences:
  * The alternating lines will not be in bold (was a bug)
  * The marker column will not be rendered with alternating background color

2. Use alternating background color when 'alt-bg' is set

  go run main.go --color bg:238,alt-bg:237
  go run main.go --color bg:238,alt-bg:237 --highlight-line

3. 'selected-bg' should take precedence

  go run main.go --color bg:238,alt-bg:237,selected-bg:232 \
                 --highlight-line --multi --bind 'load:select+up+select+up'

4. Should work with text with ANSI colors

  declare -f | perl -0777 -pe 's/^}\n/}\0/gm' |
    bat --plain --language bash --color always |
    go run main.go --read0 --ansi --reverse --multi \
                   --color bg:237,alt-bg:238,current-bg:236 --highlight-line

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Close #4354
Fix #4372

0 files changed, 0 insertions, 0 deletions