[Add battery level warning]

[Benjamin-A]

Description of task

When the battery reaches 14V there should be a warning alerting the user.
When the battery reaches 12.2V there should be a error to surface immediately, the drone will shutdown shortly.

Suggested Workflow

• [] Final message: Good bye!

Specifications

No response

Contacts

No response

Code Quality

• Every function in header files are documented (inputs/returns/exceptions)
• The project has automated tests that cover MOST of the functions and branches in functions (pytest/gtest)
• The code is documented on the wiki (provide link)