chore: fix some small issues detected by golangci-lint

But not using it as some linters are either plain incorrect (the one
suggesting to not use nil for `c.t.Context()`) or just
debatable (checking for err value is a good practice, but there are
good reasons to opt out in some cases).

console/docs.go

@@ -168,7 +168,7 @@ func (r *imageEmbedder) Transform(node *ast.Document, reader text.Reader, pc par
 		switch node := n.(type) {
 		case *ast.Image:
 			path := string(node.Destination)
-			if strings.Index(path, "/") != -1 || !strings.HasSuffix(path, ".svg") {
+			if strings.Contains(path, "/") || !strings.HasSuffix(path, ".svg") {
 				break
 			}
 			f, err := r.root.Open(path)