The Build Action needs to be set correctly when adding dts files into a Typescript project. Currently it's set as Content. It should be TypeScriptCompile.
This is thru either Adding exiting files in SolEx under the script node or copy/paste the file on the disc then include the file to the project.
This is thru either Adding exiting files in SolEx under the script node or copy/paste the file on the disc then include the file to the project.