Tiled is a a popular free level editor tool for 2D games.  Users can place down Tiles to create game levels.  Tiled has a system for tagging layers and objects with custom properties, which means it can describe levels for many different types of games.

Tiled can be found here:
http://www.mapeditor.org/

Tiled TMX Importer is a tool for bringing the open source TMX file format into Unity’s new-in-2017.2 Tilemap system.
The whole Tilemap, Objects, and Layers are imported, including referenced or bundled Tilesets (the Tile images), and Tilemap palettes are created to allow further editing inside Unity.  Since the Tile data conversion is one-to-one, gameplay scripts can perform real-time destruction or construction with the tilemap.
The custom properties are also imported, and can be read using custom user scripts to automatically generate gameplay data.

You can find the asset here:
Tiled TMX Importer