feat: add a field on command to deprecate

[joobisb]

Closes #13

Adds a field on a command to deprecate.

How to use:

&serpent.Command{
		Use:        "frobnicate",
		Short:      "Frobnicate URLs",
		Long:       "This command frobnicates URLs in the old way.",
		Deprecated: "This command will be removed in v2.0.0.",
		Options:    o.CLI(),
		Handler: func(inv *serpent.Invocation) error {
			fmt.Println("Command successfully invoked:", o.URL.String())
			return nil
		},
	}

Example deprecated command with help :

Example deprecated command:

[joobisb]

@Emyrk could you please take a look

[Emyrk]

Very reasonable 👍

This matches how cobra does it too.

[Emyrk]

I just ran go test locally. I am unsure how to get github actions running here. It all passed.

[joobisb]

@Emyrk Thanks for reviewing and merging this. What is the release cadence for serpent? Can we release a new version v0.10.0?

[Emyrk]

@joobisb I will tag it!