adding historic fires

[abdi-adel]

Aim of the Pull Request :

Adding the historic fires on both 'alerts' and 'risks' map.

More detailed info:

Adding made :

• Adding a new dataset "historic_fires.csv" in 'data' folder

• Adding a new callback in 'Callbacks related to the "Niveau de Risque" page' in main.py

• Adding two functions in utils.py : 1) get_old_fire_positions 2) build_historic_markers

• Adding some imports in utils.py

Changing made :

• Editing the callback in 'Callbacks related to the "Alertes et Infrastructures" dashboard' in main.py

• Editing the build_risks_map() function by adding the build_historic_markers in risks.py

• Editing the build_alerts_map() function by adding the build_historic_markers in alerts.py

Note 1 : No density filter

Note 2 : We will push a new version later with comments on the different functions

Thanks for reviewing