Updating Starter Games - More descriptive names

[HelperWesley]

Updating the names of objects and variables in some of the starter projects to make them less generic.

Also updating the README.md files of those starter games to better describe the mechanics and objects in the games.

[github-actions]

Preview the game(s) changed or added in this Pull Request

• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-2d-car-racing/starting-2d-car-racing.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-2d-driving/starting-2d-driving.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-2d-platformer-shooter/starting-2d-platformer-shooter.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3D-platformer/starting-3D-platformer.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-car-racing/starting-3d-car-racing.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-draggable-tiles/starting-3d-draggable-tiles.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-driving/starting-3d-driving.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-endless-runner/starting-3d-endless-runner.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-flight-sim/starting-3d-flight-sim.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-point-and-click-adventure/starting-3d-point-and-click-adventure.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-rts-unit-selection/starting-3d-rts-unit-selection.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-shootemup/starting-3d-shootemup.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-tank/starting-3d-tank.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-tile-placement/starting-3d-tile-placement.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-top-down-rpg/starting-3d-top-down-rpg.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-twin-stick-shooter/starting-3d-twin-stick-shooter.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-3d-vampire-survivor/starting-3d-vampire-survivor.json
• https://editor.gdevelop.io?project=https://raw.githubusercontent.com/GDevelopApp/GDevelop-examples/starter-game-updates/examples/starting-twin-stick-shooter/starting-twin-stick-shooter.json

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This is an automatic message displaying links to the games in this PR - double check the JSON in case of doubt.