adding reaction support (#2)

- some rework of structure to allow for more puposeful response usage
- react and response now live on the message itself
- message structs split into own file
- readme updated to use new methods

Reviewed-on: #2
Co-authored-by: jake <jake.young.dev@gmail.com>
Co-committed-by: jake <jake.young.dev@gmail.com>

command.go

@@ -1,6 +1,8 @@
 package bolt
 
-import "time"
+import (
+	"time"
+)
 
 // custom Discord commands
 type Command struct {
@@ -12,14 +14,4 @@ type Command struct {
 }
 
 // command payload functions, any strings returned are sent as a response to the command
-type Payload func(msg Message) (string, error)
-
-// message information passed to payload function
-type Message struct {
-	Author  string   //username of message author
-	ID      string   //discord ID of message author
-	Words   []string //words from message split on whitespace
-	Content string   //entire message content
-	Channel string   //message channel
-	Server  string   //message guild
-}
+type Payload func(msg Message) error