fix headings of md files

docs/modders/Map_Objects/Boat.md

@@ -1,3 +1,5 @@
+# Boat
+
 ``` javascript
 {
 	// Layer on which this boat moves. Possible values:

docs/modders/Map_Objects/Creature_Bank.md

@@ -1,3 +1,5 @@
+# Creature Bank
+
 Reward types for clearing creature bank are limited to resources, creatures, artifacts and spell.
 Format of rewards is same as in [Rewardable Objects](Rewardable.md)
 

docs/modders/Map_Objects/Dwelling.md

@@ -1,3 +1,5 @@
+# Dwelling
+
 ``` javascript
 {
 	/// List of creatures in this bank. Each list represents one "level" of bank

docs/modders/Map_Objects/Market.md

@@ -1,3 +1,5 @@
+# Market
+
 ## Market schema
 
 Since VCMI-1.3 it's possible to create customizable markets on adventure map.

docs/modders/Map_Objects/Rewardable.md

@@ -1,3 +1,5 @@
+# Rewardable
+
 ## Base object definition
 Rewardable object is defined similarly to other objects, with key difference being `handler`. This field must be set to `"handler" : "configurable"` in order for vcmi to use this mode.
 ```jsonc