Added tilemap plugin and tilemap

Assets/Plugins/codeandweb.com/Readme.txt

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+The TexturePacker Importer script (located in Assets/codeandweb.com/Editor)
+extends your Unity editor to read sprite atlas data created with TexturePacker.
+
+It automatically detects changed or newly added spritesheets written by TexturePacker
+and (re)imports them as native Unity 2D spritesheets, so that their sprites can directly
+be used in the editor. In your TexturePacker project you have to select the data format
+"Unity - Texture2D sprite sheet".
+
+TexturePacker Importer with Unity 2021.2 (or newer) requires the "Sprite 2D" package,
+please make sure that it is part of your Unity project. You can install it using
+Unity's package manager.
+
+Visit our tutorial page for more information:
+https://www.codeandweb.com/texturepacker/unity