Updated Custom campaigns (markdown)

Custom-campaigns.md

@@ -69,6 +69,89 @@ When choosing preferred aircraft, although the property is optional, it is best
 
 A best practice to follow is to set up one base per side as a transit hub. This is preferably a large airfield near the rear of the conflict (not easily captured or destroyed), that has the ability to produce ground units (has a factory), has a cargo aircraft squadron, and optionally has a port. Depending on the location of this base it may also be a good home for AEW&C and refueling squadrons (and a BARCAP squadron to defend those other squadrons).
 
+### Common issues with a custom campaign yaml file and their solutions
+
+#### 'air-to-ground' is not a valid FlightType
+
+![image](https://user-images.githubusercontent.com/89945461/133662181-aa9295d5-f9cb-4c63-9f24-f5e507164d6d.png)
+
+The following tasks can only be set as secondary tasks, not primary ones:
+* air-to-air
+* air-to-ground
+
+Incorrect:
+```
+    - primary: air-to-ground
+      secondary: any
+      aircraft:
+        - VFA-113
+```
+
+Correct:
+```
+    - primary: SEAD
+      secondary: air-to-ground
+      aircraft:
+        - VFA-113
+```
+
+#### 'primary'
+
+![image](https://user-images.githubusercontent.com/89945461/133662665-4d2a9227-5964-40ad-9430-9e24b4cb727c.png)
+
+The yaml file contains a dash before 'secondary' or other field which is not 'primary'.
+
+Incorrect:
+```
+    - primary: SEAD
+    - secondary: air-to-ground
+      aircraft:
+        - VFA-113
+```
+
+Correct:
+```
+    - primary: SEAD
+      secondary: air-to-ground
+      aircraft:
+        - VFA-113
+```
+
+#### <<class 'game.theater.controlpoint.Carrier'>: Naval-1>
+
+![image](https://user-images.githubusercontent.com/89945461/133663057-aa241157-9f8b-4271-8022-04657f0c6dfb.png)
+
+The yaml file doesn't have squadrons defined.
+
+#### 'NoneType' object is not iterable
+
+![image](https://user-images.githubusercontent.com/89945461/133663441-4834937d-b529-4d99-aa17-5bfa6bdd239b.png)
+
+The campaign yaml file contains a squadron with an 'aircraft' block, but no aircraft (or squadrons).
+
+Incorrect:
+```
+    - primary: SEAD
+      secondary: air-to-ground
+      aircraft:
+    - primary: BAI
+      secondary: any
+      aircraft:
+        - VMFA-251
+```
+
+Correct:
+```
+    - primary: SEAD
+      secondary: air-to-ground
+      aircraft:
+        - VFA-113
+    - primary: BAI
+      secondary: any
+      aircraft:
+        - VMFA-251
+```
+
 ## Designing campaigns in the mission editor
 
 When creating a campaign it may be easiest to start with an existing campaign in the same theater and modify it to suit your needs. If starting from scratch, ensure that Combined Joint Task Forces Blue and Combined Joint Task Forces Red are assigned to the blue and red coalitions respectively, as these will be used to define many of the campaigns properties.