[BUG] Custom button label

[LorhanSohaky]

Describe the bug Not uses my button label

To Reproduce Steps to reproduce the behavior:

1. Edit mkdocs.yml with:

   plugins:
   - awesome-pages
   - search
   - blogging:
     dirs:
       - blog
   
     locale: pt
     time_format: '%d/%m/%y %H:%M:%S'
     meta_time_format: '%Y-%m-%d %H:%M:%S'
     theme:
       name: button
       options:
         - plain_button: true
         - label: 'Test'
     features:
       tags:
         index_page: tags.md
         insert: top

2. Creates a blog post blog/test.md:

   
   ---
   title: Loren
   description: Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
   # Additional metadata can be used in the template
   author: User
   tags:
   - test
   ---

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

4. Creates `index.md`
```md
---
title: Home
hide:
  - navigation
---

# My posts

{{ blog_content }}

6. See error

Expected behavior Button with label Test

Screenshots

Environment (please complete the following information):

• OS: Linux
• Python version 3.7
• Plugin version 2.0.1

[liang2kl]

Sorry, this is misdocumented. The theme option should be a dictionary (object):

theme:
  name: button
  options:
    plain_button: true
    label: 'Test'

You should remove the - before plain_button and label.