feat: emoji reactions for tasks and comments (#2196)

This PR adds reactions for tasks and comments, similar to what you can do on Gitea, GitHub, Slack and plenty of other tools.

Reviewed-on: https://kolaente.dev/vikunja/vikunja/pulls/2196
Co-authored-by: kolaente <k@knt.li>
Co-committed-by: kolaente <k@knt.li>

pkg/models/models.go

@@ -61,6 +61,7 @@ func GetTables() []interface{} {
 		&APIToken{},
 		&TypesenseSync{},
 		&Webhook{},
+		&Reaction{},
 	}
 }