feat(viewport): horizontal scroll (#240)

* horizontal scroll

* rebase branch

* add tests

* add tests with 2 cells symbols

* trimLeft, move to charmbracelete/x/ansi lib

* up ansi package

* Update viewport/viewport.go

Co-authored-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>

* fix: do not navigate out to the right

* fix: cache line width on setcontent

* fix tests

* fix viewport tests

* add test for preventing right overscroll

* chore(viewport): increase horizontal step to 6

* chore(viewport): make horizontal scroll API better match vertical scroll API

* fix: nolint

* fix: use ansi.Cut

* perf: do not cut anything if not needed

* feat: expose HorizontalScrollPercent

* fix: do not scroll if width is 0

Signed-off-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>

* fix: visible lines take frame into account

---------

Signed-off-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>
Co-authored-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>
Co-authored-by: Christian Rocha <christian@rocha.is>

viewport/keymap.go

@@ -15,6 +15,8 @@ type KeyMap struct {
 	HalfPageDown key.Binding
 	Down         key.Binding
 	Up           key.Binding
+	Left         key.Binding
+	Right        key.Binding
 }
 
 // DefaultKeyMap returns a set of pager-like default keybindings.
@@ -44,5 +46,13 @@ func DefaultKeyMap() KeyMap {
 			key.WithKeys("down", "j"),
 			key.WithHelp("↓/j", "down"),
 		),
+		Left: key.NewBinding(
+			key.WithKeys("left", "h"),
+			key.WithHelp("←/h", "move left"),
+		),
+		Right: key.NewBinding(
+			key.WithKeys("right", "l"),
+			key.WithHelp("→/l", "move right"),
+		),
 	}
 }