docs(dashboard): describe each panel and give an example how to use i…

…n globalConfig file (#923)

docs/dashboard.md

@@ -17,4 +17,83 @@ As of now, 3 pre-built panels are supported:
 
 > Note: if you change the dashboard page (Edit button) after the add-on is
 > installed, the changes go to `local` folder, and you will see your version
-> of the dashboard even if you update an add-on. 
+> of the dashboard even if you update an add-on.
+
+To be able to add a dashboard page to an existing add-on, you need to adjust your 
+globalConfig file and include a new page "dashboard" there. Here is an example:
+
+```json
+{
+    "pages": {
+        "configuration": {
+            "tabs": [
+                ...
+            ],
+            "title": "Configuration",
+            "description": "Set up your add-on"
+        },
+        "inputs": {
+            "services": [
+                ...
+            ],
+            "title": "Inputs",
+            "description": "Manage your data inputs",
+            "table": {
+                ...
+            }
+        },
+        "dashboard": {
+            "panels": [
+                {
+                    "name": "addon_version"
+                },
+                {
+                    "name": "events_ingested_by_sourcetype"
+                },
+                {
+                    "name": "errors_in_the_addon"
+                }
+            ]
+        }
+    },
+    "meta": {
+      ...
+    }
+}
+```
+
+### Add-on version
+
+Executes the following search:
+
+```
+| rest services/apps/local/<addon_name> splunk_server=local | fields version
+```
+
+> Note: <addon_name> is being replaced by the actual value during the build time.
+
+### Events ingested by sourcetype
+
+Executes the following search:
+
+```
+index=_internal source=*<addon_name>* action=events_ingested
+| timechart avg(n_events) by sourcetype_ingested
+```
+
+> Note: <addon_name> is being replaced by the actual value during the build time.
+
+This search assumes specific data format in the internal logs to fill the panel with
+data.
+
+It's recommended to utilize `solnlib.log`'s [`events_ingested` function](https://github.com/splunk/addonfactory-solutions-library-python/blob/3045f9d15398fac0bd6740645ba119250ead129b/solnlib/log.py#L253).
+
+### Errors in the add-on
+
+Executes the following search:
+
+```
+index=_internal source=*<addon_name>* ERROR
+```
+
+> Note: <addon_name> is being replaced by the actual value during the build time.