Add check for missing readme in sketch

Author: per1234

check/checkconfigurations/checkconfigurations.go

@@ -1136,4 +1136,19 @@ var configurations = []Type{
 		ErrorModes:      []checkmode.Type{checkmode.Strict},
 		CheckFunction:   checkfunctions.PdeSketchExtension,
 	},
+	{
+		ProjectType:     projecttype.Sketch,
+		Category:        "structure",
+		Subcategory:     "",
+		ID:              "",
+		Brief:           "no readme",
+		Description:     "",
+		MessageTemplate: "No readme found. Please document your sketch. See: https://docs.github.com/en/free-pro-team@latest/github/creating-cloning-and-archiving-repositories/about-readmes",
+		DisableModes:    nil,
+		EnableModes:     []checkmode.Type{checkmode.Default},
+		InfoModes:       nil,
+		WarningModes:    []checkmode.Type{checkmode.Default},
+		ErrorModes:      []checkmode.Type{checkmode.Strict},
+		CheckFunction:   checkfunctions.MissingReadme,
+	},
 }