Extend: Ensure MIME string normalization (#756)

* ensure MIME string normalization in Extend()

* use stdmime alias because mime is overloaded

---------

Co-authored-by: Gabriel Vasile <gabriel.vasile@email.com>

Author: yzqzss

mime.go

@@ -1,7 +1,7 @@
 package mimetype
 
 import (
-	"mime"
+	stdmime "mime"
 	"slices"
 	"strings"
 
@@ -52,8 +52,8 @@ func (m *MIME) Parent() *MIME {
 func (m *MIME) Is(expectedMIME string) bool {
 	// Parsing is needed because some detected MIME types contain parameters
 	// that need to be stripped for the comparison.
-	expectedMIME, _, _ = mime.ParseMediaType(expectedMIME)
-	found, _, _ := mime.ParseMediaType(m.mime)
+	expectedMIME, _, _ = stdmime.ParseMediaType(expectedMIME)
+	found, _, _ := stdmime.ParseMediaType(m.mime)
 
 	if expectedMIME == found {
 		return true
@@ -196,6 +196,7 @@ func (m *MIME) lookup(mime string) *MIME {
 // The sub-format will be detected if all the detectors in the parent chain return true.
 // The extension should include the leading dot, as in ".html".
 func (m *MIME) Extend(detector func(raw []byte, limit uint32) bool, mime, extension string, aliases ...string) {
+	mime, _, _ = stdmime.ParseMediaType(mime)
 	c := &MIME{
 		mime:      mime,
 		extension: extension,

mimetype_test.go

@@ -748,6 +748,7 @@ func TestExtend(t *testing.T) {
 		{"foo", ".foo", nil},
 		{"bar", ".bar", root},
 		{"baz", ".baz", zip},
+		{" UperCaseWithWhiteSpace/a+B; key=val   ", ".upercase", nil},
 	}
 
 	for _, tt := range data {