Documentation for the API

[naipotato]

This PR adds documentation to the library

Task list:

• Document the class itself
• Document the public constructor
• Document all the public methods
• Document ContainerFactoryFunc
• Add docs generation task to build system
• Add docs as a boolean option on meson_options.txt
• Update README with the new syntax

[codecov]

Codecov Report

Merging #5 into main will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##              main        #5   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files            1         1           
  Lines           79        79           
=========================================
  Hits            79        79           

Impacted Files	Coverage Δ
lib/vadi-container.vala	100.00% <ø> (ø)

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