Some doc to bevy_diagnostic (#11020)

Author: stepancheg

crates/bevy_diagnostic/src/entity_count_diagnostics_plugin.rs

@@ -3,7 +3,11 @@ use bevy_ecs::entity::Entities;
 
 use crate::{Diagnostic, DiagnosticId, Diagnostics, RegisterDiagnostic};
 
-/// Adds "entity count" diagnostic to an App
+/// Adds "entity count" diagnostic to an App.
+///
+/// # See also
+///
+/// [`LogDiagnosticsPlugin`](crate::LogDiagnosticsPlugin) to output diagnostics to the console.
 #[derive(Default)]
 pub struct EntityCountDiagnosticsPlugin;
 

crates/bevy_diagnostic/src/frame_time_diagnostics_plugin.rs

@@ -5,6 +5,10 @@ use bevy_ecs::prelude::*;
 use bevy_time::{Real, Time};
 
 /// Adds "frame time" diagnostic to an App, specifically "frame time", "fps" and "frame count"
+///
+/// # See also
+///
+/// [`LogDiagnosticsPlugin`](crate::LogDiagnosticsPlugin) to output diagnostics to the console.
 #[derive(Default)]
 pub struct FrameTimeDiagnosticsPlugin;
 

crates/bevy_diagnostic/src/log_diagnostics_plugin.rs

@@ -5,7 +5,13 @@ use bevy_log::{debug, info};
 use bevy_time::{Real, Time, Timer, TimerMode};
 use bevy_utils::Duration;
 
-/// An App Plugin that logs diagnostics to the console
+/// An App Plugin that logs diagnostics to the console.
+///
+/// Diagnostics are collected by plugins such as
+/// [`FrameTimeDiagnosticsPlugin`](crate::FrameTimeDiagnosticsPlugin)
+/// or can be provided by the user.
+///
+/// When no diagnostics are provided, this plugin does nothing.
 pub struct LogDiagnosticsPlugin {
     pub debug: bool,
     pub wait_duration: Duration,

crates/bevy_diagnostic/src/system_information_diagnostics_plugin.rs

@@ -10,6 +10,10 @@ use bevy_app::prelude::*;
 /// * macos
 ///
 /// NOT supported when using the `bevy/dynamic` feature even when using previously mentioned targets
+///
+/// # See also
+///
+/// [`LogDiagnosticsPlugin`](crate::LogDiagnosticsPlugin) to output diagnostics to the console.
 #[derive(Default)]
 pub struct SystemInformationDiagnosticsPlugin;
 impl Plugin for SystemInformationDiagnosticsPlugin {