Add description to linger_timeout behavior about Windows

This option is added in fluent/fluentd#3644
The description is added in fluent#392

However, there was a lack of consideration regarding the default
behavior on Windows.

Signed-off-by: Daijiro Fukuda <fukuda@clear-code.com>

Author: daipom

input/forward.md

@@ -170,9 +170,11 @@ This section is for setting TLS transport or some general transport configuratio
 
 The timeout \(seconds\) to set `SO_LINGER`.
 
-The default value `0` is to send RST rather than FIN to avoid lots of connections sitting in TIME_WAIT on closing.
+The default value `0` is to send RST rather than FIN to avoid lots of connections sitting in TIME_WAIT on closing on non-Windows.
 
-You can set positive value to send FIN on closing.
+You can set positive value to send FIN on closing on non-Windows.
+
+(On Windows, Fluentd sends FIN when `linger_timeout` is `0` too).
 
 ```text
 <transport tcp>

input/http.md

@@ -178,9 +178,11 @@ This section is for setting TLS transport or some general transport configuratio
 
 The timeout \(seconds\) to set `SO_LINGER`.
 
-The default value `0` is to send RST rather than FIN to avoid lots of connections sitting in TIME_WAIT on closing.
+The default value `0` is to send RST rather than FIN to avoid lots of connections sitting in TIME_WAIT on closing on non-Windows.
 
-You can set positive value to send FIN on closing.
+You can set positive value to send FIN on closing on non-Windows.
+
+(On Windows, Fluentd sends FIN when `linger_timeout` is `0` too).
 
 ```text
 <transport tcp>

input/tcp.md

@@ -151,9 +151,11 @@ This section is for setting TLS transport or some general transport configuratio
 
 The timeout \(seconds\) to set `SO_LINGER`.
 
-The default value `0` is to send RST rather than FIN to avoid lots of connections sitting in TIME_WAIT on closing.
+The default value `0` is to send RST rather than FIN to avoid lots of connections sitting in TIME_WAIT on closing on non-Windows.
 
-You can set positive value to send FIN on closing.
+You can set positive value to send FIN on closing on non-Windows.
+
+(On Windows, Fluentd sends FIN when `linger_timeout` is `0` too).
 
 ```text
 <source>

plugin-helper-overview/api-plugin-helper-server.md

@@ -170,9 +170,11 @@ end
 
 The timeout \(seconds\) to set `SO_LINGER`.
 
-The default value `0` is to send RST rather than FIN to avoid lots of connections sitting in TIME_WAIT on closing.
+The default value `0` is to send RST rather than FIN to avoid lots of connections sitting in TIME_WAIT on closing on non-Windows.
 
-You can set positive value to send FIN on closing.
+You can set positive value to send FIN on closing on non-Windows.
+
+(On Windows, Fluentd sends FIN when `linger_timeout` is `0` too).
 
 ```text
 <source>