graph visualisation

[gitond]

Using the SMFL library ( https://www.sfml-dev.org/index.php ) to visualise graphs

• [x] File struture for visualisation
• [x] Attempt to make sfml co-operate with github actions
• [x] Visualisation feature: draw dots with sfml
• [x] Visualisation feature: draw lines with sfml
• [x] figure out how to render text on image (label vertices and edges)
• [x] Synchronize visualisation with the graph class so that visualization function can take graph as input and draw it --- Need to do #24 or #25 before progress possible ---
• [x] Edit function so that edges between certain vertices can be colored differently (highlight path)
• [x] Give the several edge coloring options (highlight searched)
• [x] Visualisation feature: save images to file using sfml sf::Image ( https://www.sfml-dev.org/documentation/2.5.1/classsf_1_1Image.php )
• [ ] Examine opportunity of autogenerating images and getting them out of GitHub Actions on push
• [x] Connect with cli #20

[gitond]

Added optional issue for better style at #26

[gitond]

26 changed to be a generic file for new features that would improve the usability of graph visualization, but which are not necessary for the project