Refine WriteToTempFile docstring

Clarify the documentation for WriteToTempFile to better explain its functionality, ensure consistency, and detail its return values.

msg_totmpfile.go

@@ -12,8 +12,14 @@ import (
  "os"
 )
 
-// WriteToTempFile will create a temporary file and output the Msg to this file
-// The method will return the filename of the temporary file
+// WriteToTempFile creates a temporary file and writes the Msg content to this file.
+//
+// This method generates a temporary file with a ".eml" extension, writes the Msg to it, and returns the
+// filename of the created temporary file.
+//
+// Returns:
+// - A string representing the filename of the temporary file.
+// - An error if the file creation or writing process fails.
 func (m *Msg) WriteToTempFile() (string, error) {
  f, err := os.CreateTemp("", "go-mail_*.eml")
  if err != nil {

msg_totmpfile_116.go

@@ -12,8 +12,14 @@ import (
  "io/ioutil"
 )
 
-// WriteToTempFile will create a temporary file and output the Msg to this file
-// The method will return the filename of the temporary file
+// WriteToTempFile creates a temporary file and writes the Msg content to this file.
+//
+// This method generates a temporary file with a ".eml" extension, writes the Msg to it, and returns the
+// filename of the created temporary file.
+//
+// Returns:
+// - A string representing the filename of the temporary file.
+// - An error if the file creation or writing process fails.
 func (m *Msg) WriteToTempFile() (string, error) {
  f, err := ioutil.TempFile("", "go-mail_*.eml")
  if err != nil {