docs(vrl): add docs for new timezone option in parse_timestamp func…

…tion (#22121)

* Add new `timezone` option for `parse_timestamp` function

* Add more explain to the timezone argument in doc

* Update website/cue/reference/remap/functions/parse_timestamp.cue

Co-authored-by: Brett Blue <84536271+brett0000FF@users.noreply.github.com>

* Add more failed reason

* Fix example without DST

---------

Co-authored-by: Brett Blue <84536271+brett0000FF@users.noreply.github.com>
Co-authored-by: Pavlos Rontidis <pavlos.rontidis@gmail.com>

website/cue/reference/remap/functions/parse_timestamp.cue

@@ -19,10 +19,19 @@ remap: functions: parse_timestamp: {
 			required:    true
 			type: ["string"]
 		},
-
+		{
+			name:        "timezone"
+			description: """
+				The [TZ database](\(urls.tz_time_zones)) format. By default, this function parses the timestamp by global [`timezone` option](\(urls.vector_configuration)/global-options#timezone).
+				This argument overwrites the setting and is useful for parsing timestamps without a specified timezone, such as `16/10/2019 12:00:00`.
+				"""
+			required:    false
+			type: ["string"]
+		},
 	]
 	internal_failure_reasons: [
 		"`value` fails to parse using the provided `format`.",
+		"`value` fails to parse using the provided `timezone`.",
 	]
 	return: types: ["timestamp"]
 
@@ -34,5 +43,12 @@ remap: functions: parse_timestamp: {
 				"""#
 			return: "2020-10-10T16:00:00Z"
 		},
+		{
+			title: "Parse timestamp with timezone"
+			source: #"""
+				parse_timestamp!("16/10/2019 12:00:00", format: "%d/%m/%Y %H:%M:%S", timezone: "Asia/Taipei")
+				"""#
+			return: "2019-10-16T04:00:00Z"
+		},
 	]
 }