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>

message.go

@@ -0,0 +1,57 @@
+package bolt
+
+import "fmt"
+
+//built-in Discord reactions
+type Reaction string
+
+const (
+	ReactionThumbsUp      Reaction = ":+1:"
+	ReactionThumbsDown    Reaction = ":-1:"
+	ReactionPointUp       Reaction = ":point_up:"
+	ReactionPointDown     Reaction = ":point_down:"
+	ReactionHotdog        Reaction = ":hotdog:"
+	ReactionGiraffe       Reaction = ":giraffe:"
+	ReactionWatermelon    Reaction = ":watermelon:"
+	ReactionNoPedestrians Reaction = ":no_pedestrian:"
+)
+
+// information about attachments to messages
+type MessageAttachment struct {
+	ID           string
+	URL          string
+	ProxyURL     string
+	Filename     string
+	ContentType  string
+	Width        int
+	Height       int
+	Size         int
+	DurationSecs float64
+}
+
+// represents a Discord message
+type Message struct {
+	Author      string   //username of message author
+	ID          string   //discord ID of message author
+	msgID       string   //id string of message
+	Words       []string //words from message split on whitespace
+	Content     string   //entire message content
+	Channel     string   //message channel
+	channelID   string   //id of channel message was sent in
+	Server      string   //message guild
+	serverID    string   //id of guild message was sent in
+	Attachments []MessageAttachment
+	sesh        *bolt
+}
+
+// applies reaction to message
+func (m *Message) React(emoji Reaction) error {
+	return m.sesh.MessageReactionAdd(m.channelID, m.msgID, fmt.Sprint(emoji))
+}
+
+// sends the value of res in response to the message
+func (m *Message) Respond(res string) error {
+	rep := m.sesh.createReply(res, m.msgID, m.channelID, m.serverID)
+	_, err := m.sesh.ChannelMessageSendComplex(m.channelID, rep)
+	return err
+}