WCAG-A accessibility

Description

This PR contains a set of markup changes that are required in order to achieve level A score on WCAG 2.0

Type of PR This PR is a [improvement].

Screenshots

Not Applicable as the markup generates the same output.

Checklist:

• My pull request has a descriptive title (not a vague title like "Update index.md").
• My pull request targets the phoenix/develop branch of the repository.
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible errors.