Add attributes for HTML tags

[ericanaughton]

In order to understand HTML, As a Spanish or English LMHT user, I want to learn about the attributes of HTML tags.

Acceptance Criteria:

• Commonly used attributes are represented
• Attributes are defined and translated
• Attributes have a 'How to remember' tips
• Audio recordings of attributes are available
• Code example of attributes
• Attributes are displayed in an organized, simplified manner

Given a Spanish or English user, When I view all the HTML tags, I should also see common attributes And learn about the attributes through definitions, translations, audio, tips and code examples.

[ericanaughton]

Possibilities:

• Attributes can be displayed as subcategories in the dropdown list
• Attributes and Tags can be displayed in a text editor style reference side bar (see https://github.com/LMHT/LMHT.github.io/issues/76)