Chore: Refactor error handling and resource management across multiple files (golangci-lint)

- Updated error handling to use the error return value for resource closures in tests and functions, ensuring proper error reporting.
- Replaced direct calls to `Close()` with deferred functions that handle errors gracefully.
- Improved readability by using `strings.ReplaceAll` instead of `strings.Replace` for string manipulation.
- Enhanced network connection handling by adding default cases for unsupported network types.
- Updated HTTP response handling to use the appropriate status codes and error messages.
- Removed unused variables and commented-out code to clean up the codebase.

internal/htmlcheck/css.go

@@ -193,10 +193,10 @@ func downloadToBytes(url string) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
-	defer resp.Body.Close()
+	defer func() { _ = resp.Body.Close() }()
 
 	if resp.StatusCode != 200 {
-		err := fmt.Errorf("Error downloading %s", url)
+		err := fmt.Errorf("error downloading %s", url)
 		return nil, err
 	}
 

internal/htmlcheck/main.go

@@ -152,13 +152,14 @@ func (c CanIEmail) getTest(k string) (Warning, error) {
 				s.Platform = platform
 				s.Version = version
 
-				if support == "y" {
+				switch support {
+				case "y":
 					y++
 					s.Support = "yes"
-				} else if support == "n" {
+				case "n":
 					n++
 					s.Support = "no"
-				} else {
+				default:
 					p++
 					s.Support = "partial"