Add doc files to .sln

Author: toebeann

Tobey.UnityAudio.sln

@@ -18,6 +18,13 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "build", "build", "{F47EDC2F
 		manifest.json = manifest.json
 	EndProjectSection
 EndProject
+Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "docs", "docs", "{CCEB055D-4909-4888-9682-ACC4CD66F06C}"
+	ProjectSection(SolutionItems) = preProject
+		CHANGELOG.md = CHANGELOG.md
+		LICENSE = LICENSE
+		README.md = README.md
+	EndProjectSection
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU