Extract parameters from slam_gmapping.cpp to slam_gmapping_params.yaml to be configurable

[wafaa216]

• Extract parameters from slam_gmapping.cpp to slam_gmapping_params.yaml to be configurable
• Edit slam_gmapping.cpp to have declaration for these parameters and get them to be used in the code
• Test with turtlebot3
• Edit Readme

[AbdelrahmanEldesouky]

Thank you for extracting the parameters from slam_gmapping.cpp into slam_gmapping_params.yaml. It was a headache to edit them directly in the code! This change significantly enhances flexibility and makes it much easier to fine-tune the parameters for different scenarios in my project.