Add support for custom key macros (#217)

docs/example_config.json

@@ -2,7 +2,7 @@
 	"default_profile": "default",
 	"profiles": {
 		"default": {
-			"user_id":  "",
+			"user_id":  "@user:matrix.org",
 			"url":      "https://matrix.org",
 			"settings": {},
 			"dirs":     {}
@@ -34,6 +34,14 @@
 			}
 		}
 	},
+	"layout": {
+		"style": "restore"
+	},
+	"macros": {
+		"i": {
+			"jj": "<Esc>"
+		}
+	},
 	"dirs": {
 		"cache":     "/home/user/.cache/iamb/",
 		"logs":      "/home/user/.local/share/iamb/logs/",