Add MD5 back to template helper functions to avoid breaking (go-gitea#21102)

In go-gitea#20932 the MD5 helper function was removed from template context,
it breaks user's customized templates.

This PR adds the MD5 helper function back.

Author: tyroneyeh

modules/templates/helper.go

@@ -154,6 +154,7 @@ func NewFuncMap() []template.FuncMap {
 		"DiffTypeToStr":                  DiffTypeToStr,
 		"DiffLineTypeToStr":              DiffLineTypeToStr,
 		"ShortSha":                       base.ShortSha,
+		"MD5":                            base.EncodeMD5,
 		"ActionContent2Commits":          ActionContent2Commits,
 		"PathEscape":                     url.PathEscape,
 		"PathEscapeSegments":             util.PathEscapeSegments,