优化

app/src/main/assets/help/httpTTSHelp.md

@@ -4,7 +4,7 @@
 * js参数
 ```
 speakText //朗读文本
-speakSpeed //朗读速度,0-45
+speakSpeed //朗读速度,5-50
 ```
 * 例:
 ```

app/src/main/java/io/legado/app/ui/book/read/config/ReadAloudDialog.kt

@@ -115,12 +115,12 @@ class ReadAloudDialog : BaseDialogFragment(R.layout.dialog_read_aloud) {
         }
         ivTtsSpeechReduce.setOnClickListener {
             seekTtsSpeechRate.progress = AppConfig.ttsSpeechRate - 1
-            AppConfig.ttsSpeechRate = AppConfig.ttsSpeechRate - 1
+            AppConfig.ttsSpeechRate -= 1
             upTtsSpeechRate()
         }
         ivTtsSpeechAdd.setOnClickListener {
             seekTtsSpeechRate.progress = AppConfig.ttsSpeechRate + 1
-            AppConfig.ttsSpeechRate = AppConfig.ttsSpeechRate + 1
+            AppConfig.ttsSpeechRate += 1
             upTtsSpeechRate()
         }
         ivTimer.setOnClickListener {