Add --color flag

Flag `--color` forces colored output, even if stdout is not a terminal.

Motivation
- `grep --color=always`
- `ls --color=always`

Application
- Allows colored text when piping to tools like fzf outside of `zk list --interactive`

main.go

@@ -12,6 +12,7 @@ import (
 	"strings"
 
 	"github.com/alecthomas/kong"
+	"github.com/fatih/color"
 	"github.com/zk-org/zk/internal/cli"
 	"github.com/zk-org/zk/internal/cli/cmd"
 	"github.com/zk-org/zk/internal/core"
@@ -31,9 +32,10 @@ var root struct {
 	Edit  cmd.Edit  `cmd group:"notes" help:"Edit notes matching the given criteria."`
 	Tag   cmd.Tag   `cmd group:"notes" help:"Manage the note tags."`
 
-	NotebookDir string  `type:path placeholder:PATH help:"Turn off notebook auto-discovery and set manually the notebook where commands are run."`
-	WorkingDir  string  `short:W type:path placeholder:PATH help:"Run as if zk was started in <PATH> instead of the current working directory."`
-	NoInput     NoInput `help:"Never prompt or ask for confirmation."`
+	NotebookDir string     `type:path placeholder:PATH help:"Turn off notebook auto-discovery and set manually the notebook where commands are run."`
+	WorkingDir  string     `short:W type:path placeholder:PATH help:"Run as if zk was started in <PATH> instead of the current working directory."`
+	NoInput     NoInput    `help:"Never prompt or ask for confirmation."`
+	Color       ForceColor `help:"Force colored output"`
 	// ForceInput is a debugging flag overriding the default value of interaction prompts.
 	ForceInput string `hidden xor:"input"`
 	Debug      bool   `default:"0" hidden help:"Print a debug stacktrace on SIGINT."`
@@ -52,6 +54,14 @@ func (f NoInput) BeforeApply(container *cli.Container) error {
 	return nil
 }
 
+// When enabled, output colored text even if stdout is not a tty.
+type ForceColor bool
+
+func (c ForceColor) BeforeApply() error {
+	color.NoColor = false
+	return nil
+}
+
 // ShowHelp is the default command run. It's equivalent to `zk --help`.
 type ShowHelp struct{}