[fix] Fix VBA code block display error

[ramsayleung]

Issue

修复第五章 VBA 代码展示问题, 原来的markdown 文档使用了 <img src="/images/speech-tract-$1.svg" class="themed" />样式, 导致 Github Markdown 无法正常渲染:

<img src="/images/speech-tract-$1.svg" class="themed" />Sub SpeakText()
<img src="/images/speech-tract-$1.svg" class="themed" />    On Error Resume Next
<img src="/images/speech-tract-$1.svg" class="themed" />    Set speech = New SpVoice
<img src="/images/speech-tract-$1.svg" class="themed" />    Selection.MoveLeft Unit:=wdWord, Count:=1
<img src="/images/speech-tract-$1.svg" class="themed" />    Selection.MoveRight Unit:=wdWord, Count:=1, Extend:=wdExtend
<img src="/images/speech-tract-$1.svg" class="themed" />    If Len(Selection.Text) > 1 Then
<img src="/images/speech-tract-$1.svg" class="themed" />        speech.Speak Trim(Selection.Text), SVSFlagsAsync + SVSFPurgeBeforeSpeak
<img src="/images/speech-tract-$1.svg" class="themed" />    End If
<img src="/images/speech-tract-$1.svg" class="themed" />    Selection.MoveRight Unit:=wdWord, Count:=1
<img src="/images/speech-tract-$1.svg" class="themed" />    Do
<img src="/images/speech-tract-$1.svg" class="themed" />        DoEvents
<img src="/images/speech-tract-$1.svg" class="themed" />    Loop Until speech.WaitUntilDone(10)
<img src="/images/speech-tract-$1.svg" class="themed" />    Set speech = Nothing
<img src="/images/speech-tract-$1.svg" class="themed" />End Sub

Solution

使用 markdown 的 code block 语法代替 <img src="/images/speech-tract-$1.svg" class="themed" /> 样式, 效果如下: