title: Change title color of bootstrap vue tab title
body: <p>I'm using bootstrap-vue.js to create a tab. The result is like this
  <a href="https://i.stack.imgur.com/EW76k.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EW76k.png" alt="enter image description here" /></a></p>
  <p>I just want change the tab title color because it's using default color from my project. And from the bootstrap-vue.js official link (<a href="https://bootstrap-vue.js.org/docs/components/tabs" rel="nofollow noreferrer">https://bootstrap-vue.js.org/docs/components/tabs</a>) there is a title-item-class for making any change in the tab title. So I crate the code like this :</p>
  <pre><code>&lt;b-tab title=&quot;Transaction History&quot; title-item-class=&quot;tab-title-class&quot;&gt;
  </code></pre>
  <p>and my css :</p>
  <pre><code>.tab-title-class {
      color: #FF0000 !important;  
  }
  </code></pre>
  <p>But it doesn't give any effect. So what is the problem here ?
  Thanks in advance.</p>