doc: Use the doxygen awesome theme

[realstealthninja]

Description of Change

Our doxygen website is fine but it needs a touch of modernity,
I've added the doxygen-awesome theme with a few extensions.

Main changes

• added doxygen theme
• reduced reliance on cmake for doxygen configs
• use doxyfile for doxygen config
• add favicon and project icon

comparison

old	new

Checklist

• Added description of change
• Added file name matches File name guidelines
• [ ] Added tests and example, test must pass
• [ ] Added documentation so that the program is self-explanatory and educational - Doxygen guidelines
• Relevant documentation/comments is changed or added
• PR title follows semantic commit guidelines
• Search previous suggestions before making a new one, as yours may be a duplicate.
• I acknowledge that all my contributions will be made under the project's license.

Notes:

[realstealthninja]

Want to have a browse of my implemented changes?
for the new website visit https://realstealthninja.github.io/C-Plus-Plus/
for the old website visit https://thealgorithms.github.io/C-Plus-Plus/