Updated entities and json structs for API v2.6.0

Added missing fields to various structs and sorted them in the same order as
the original mastodon API documentation does. This should make it easier to
compare go-mastodon's structs with the original documentation.

accounts.go

@@ -136,12 +136,16 @@ func (c *Client) GetBlocks(ctx context.Context, pg *Pagination) ([]*Account, err
 
 // Relationship hold information for relation-ship to the account.
 type Relationship struct {
-	ID         ID   `json:"id"`
-	Following  bool `json:"following"`
-	FollowedBy bool `json:"followed_by"`
-	Blocking   bool `json:"blocking"`
-	Muting     bool `json:"muting"`
-	Requested  bool `json:"requested"`
+	ID                  ID   `json:"id"`
+	Following           bool `json:"following"`
+	FollowedBy          bool `json:"followed_by"`
+	Blocking            bool `json:"blocking"`
+	Muting              bool `json:"muting"`
+	MutingNotifications bool `json:"muting_notifications"`
+	Requested           bool `json:"requested"`
+	DomainBlocking      bool `json:"domain_blocking"`
+	ShowingReblogs      bool `json:"showing_reblogs"`
+	Endorsed            bool `json:"endorsed"`
 }
 
 // AccountFollow follow the account.