New example: City Builder

[D8H]

This example shows how to evaluate distance by roads to define rules for city builders.

This example use these extensions:

• an updated Linked Object Tool that allows to get the distance and combine several search to build complex rules (https://github.com/4ian/GDevelop-extensions/issues/144).
• the Isometry Helper to snap objects on a grid (https://github.com/4ian/GDevelop-extensions/issues/102)
• the Mouse Movement without any change (https://github.com/4ian/GDevelop-extensions/issues/123)

The original discussion: https://github.com/4ian/GDevelop/issues/2638

Checklist

• [x] My game has a proper name in the game properties.
• [x] My game package name behind with com.example..
• [x] My game has all events unfolded.
• [x] I've added myself as the author in the game properties.
• [x] I've included a file called "README.md" with a description in proper English, explaining what this example is doing.
• [x] I confirm that this game and all of its resources can be integrated to this GitHub repository, distributed and MIT licensed.
• [x] I've cleaned unused resources.

Game folder

• download it: https://www.dropbox.com/s/6wwjfg75pyqm1qz/CityBuilder.zip?dl=1
• try it: https://games.gdevelop-app.com/game-143f99ba-13aa-4378-b1c3-50ce38efbb20/index.html

[Midhil457]

Great, I created a PR for this. I made a separate comment for the help link

Thank you for taking your time and making this example :)

[Bouh]

Let's continue to talk on the pull request :)