add example SQLite queries for use with Grafana to plot data from SQLite metrics;

docs/Example SQLite Queries for Grafana.md

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+# Example SQLite Queries for Grafana
+
+## Overview
+
+This document contains a few example SQLite queries usable with Grafana to create metrics visualizations. These are examples and no support is given for them, they were all generated
+against Grafana 11.
+
+## Examples
+
+### Example 1: Completed Call Events
+
+- Visualization: Gauge
+
+Query:
+```sql
+WITH bounds AS (
+  SELECT
+    ($__from * 1000000) AS start_ns,
+    ($__to * 1000000) AS stop_ns
+)
+SELECT COUNT(*) AS complete_call_event
+FROM call_event c, bounds b
+WHERE c.ts_ns >= b.start_ns
+  AND c.ts_ns < b.stop_ns;
+```
+
+### Example 2: Active Talkgroup Count
+
+- Visualization: Gauge
+
+Query:
+```sql
+WITH bounds AS (
+  SELECT
+    ($__from * 1000000) AS start_ns,
+    ($__to * 1000000) AS stop_ns
+)
+SELECT COUNT(DISTINCT c.dst_id) AS "Active TG Count"
+FROM call_event c, bounds b
+WHERE c.ts_ns >= b.start_ns
+AND c.ts_ns < b.stop_ns;
+```
+
+### Example 3: Active RID Count
+
+- Visualization; Gauge
+
+Query:
+```sql
+WITH bounds AS (
+  SELECT
+    ($__from * 1000000) AS start_ns,
+    ($__to * 1000000) AS stop_ns
+)
+SELECT COUNT(DISTINCT c.src_id) AS "Active RID Count"
+FROM call_event c, bounds b
+WHERE c.ts_ns >= b.start_ns
+AND c.ts_ns < b.stop_ns;
+```
+
+### Example 4: Call Volume
+
+- Visualization: Time Series
+
+Query:
+```sql
+WITH bounds AS (
+  SELECT
+    ($__from / 1000) AS start_ns,
+    ($__to / 1000) AS stop_ns
+)
+SELECT
+  CAST(ts_s / 300 AS INTEGER) * 300 AS time,
+  COUNT(*) AS "Call Volume"
+FROM call_event, bounds b
+WHERE ts_s BETWEEN b.start_ns AND b.stop_ns
+GROUP BY time
+ORDER BY time;
+```