Upgrade the document about how to collect logs for systemd and docker (#21101)

Many users (#21099) do not know how to collect logs if they are using
systemd. This PR makes the document more clear.

docs/content/doc/advanced/logging-documentation.en-us.md

@@ -15,12 +15,14 @@ menu:
 
 # Logging Configuration
 
-The logging framework has been revamped in Gitea 1.9.0.
-
 **Table of Contents**
 
 {{< toc >}}
 
+## Collecting Logs for Help
+
+To collect logs for help and issue report, see [Support Options]({{< relref "doc/help/seek-help.en-us.md" >}}).
+
 ## Log Groups
 
 The fundamental thing to be aware of in Gitea is that there are several

docs/content/doc/help/faq.en-us.md

@@ -392,7 +392,9 @@ Gitea requires the system or browser to have one of the supported Emoji fonts in
 
 Stdout on systemd goes to the journal by default. Try using `journalctl`, `journalctl  -u gitea`, or `journalctl <path-to-gitea-binary>`.
 
-Similarly stdout on docker can be viewed using `docker logs <container>`
+Similarly, stdout on docker can be viewed using `docker logs <container>`.
+
+To collect logs for help and issue report, see [Support Options]({{< relref "doc/help/seek-help.en-us.md" >}}).
 
 ## Initial logging
 
@@ -413,7 +415,7 @@ unchanged in the database schema. This may lead to warning such as:
 2020/08/02 11:32:29 ...rm/session_schema.go:360:Sync2() [W] Table user Column keep_activity_private db default is , struct default is 0
 ```
 
-These can safely be ignored but you may able to stop these warnings by getting Gitea to recreate these tables using:
+These can safely be ignored, but you are able to stop these warnings by getting Gitea to recreate these tables using:
 
 ```
 gitea doctor recreate-table user

docs/content/doc/help/seek-help.en-us.md

@@ -22,12 +22,14 @@ menu:
 
 1. Your `app.ini` (with any sensitive data scrubbed as necessary).
 2. The Gitea logs, and any other appropriate log files for the situation.
-    - The logs are likely to be outputted to console. If you need to collect logs from files,
+    - When using systemd, use `journalctl --lines 1000 --unit gitea` to collect logs.
+    - When using docker, use `docker logs --tail 1000 <gitea-container>` to collect logs.
+    - By default, the logs are outputted to console. If you need to collect logs from files,
       you could copy the following config into your `app.ini` (remove all other `[log]` sections),
       then you can find the `*.log` files in Gitea's log directory (default: `%(GITEA_WORK_DIR)/log`).
 
     ```ini
-    ; To show all SQL logs, you can also set LOG_SQL=true in the [database] section 
+    ; To show all SQL logs, you can also set LOG_SQL=true in the [database] section
     [log]
     LEVEL=debug
     MODE=console,file