feat: Added GetTeams Method

[Zozman]

Added support for the GET /teams Helix API method with a GetTeams client method.

Example Usage:

client, err := helix.NewClient(&helix.Options{
    ClientID: "your-client-id",
})
if err != nil {
    // handle error
}

resp, err := client.GetTeams(&helix.GetTeamsParams{
    Name: "weightedblanket",
})
if err != nil {
    // handle error
}

fmt.Printf("%+v\n", resp)

Includes:

• Implementation
• Unit Test
• Docs with example usage

Let me know if anything else is needed.