Should remove <auto-textarea> font size settings

[hefengxian]

I think this line has caused user can't define the edit area font size themself

这行代码导致无法自定义、覆写编辑区域的文字大小，应该删除这种设置

mavonEditor/src/mavon-editor.vue

Line 24 in b3533cf

class="content-input" fontSize="15px"

浏览器里生成的结果：

<div data-v-7a63e4b3="" class="auto-textarea-wrapper content-input" style="font-size: 15px; line-height: 1.5;">
    <pre class="auto-textarea-block" style="font-size: 15px; line-height: 1.5;"><br> </pre> 
    <textarea spellcheck="false" placeholder="开始编辑..." class="auto-textarea-input no-border no-resize" style="font-size: 15px; line-height: 1.5;"></textarea>
</div>

无法通过简单的覆盖 CSS 来解决字体样式的问题

[hinesboy]

v2.5.3 添加props: fontSize

[hefengxian]

O(∩_∩)O谢谢