Bug 1678635: Link from metrics pages to RLB API docs (#1335)

docs/user/metrics/boolean.md

@@ -163,3 +163,4 @@ assert!(flags::a11y_enabled.test_get_value(None).unwrap());
 * [Kotlin API docs](../../../javadoc/glean/mozilla.telemetry.glean.private/-boolean-metric-type/index.html)
 * [Swift API docs](../../../swift/Classes/BooleanMetricType.html)
 * [Python API docs](../../../python/glean/metrics/boolean.html)
+* [Rust API docs](../../../docs/glean/private/boolean/struct.BooleanMetric.html)

docs/user/metrics/counter.md

@@ -200,3 +200,4 @@ assert_eq!(
 * [Kotlin API docs](../../../javadoc/glean/mozilla.telemetry.glean.private/-counter-metric-type/index.html)
 * [Swift API docs](../../../swift/Classes/CounterMetricType.html)
 * [Python API docs](../../../python/glean/metrics/counter.html)
+* [Rust API docs](../../../docs/glean/private/counter/struct.CounterMetric.html)

docs/user/metrics/uuid.md

@@ -178,3 +178,4 @@ assert_eq!(u, user::client_id.test_get_value(None).unwrap());
 * [Kotlin API docs](../../../javadoc/glean/mozilla.telemetry.glean.private/-uuid-metric-type/index.html).
 * [Swift API docs](../../../swift/Classes/UuidMetricType.html)
 * [Python API docs](../../../python/glean/metrics/uuid.html)
+* [Rust API docs](../../../docs/glean/private/uuid/struct.UuidMetric.html)