Fix EOL handling in web editor (#27141)

Fixes https://github.com/go-gitea/gitea/issues/27136.

This does the following for Monaco's EOL setting:

1. Use editorconfig setting if present
2. Use the file's dominant line ending as detected by monaco, which uses
LF for empty file

routers/web/repo/editor.go

@@ -287,7 +287,7 @@ func editFilePost(ctx *context.Context, form forms.EditRepoFileForm, isNewFile b
 				Operation:     operation,
 				FromTreePath:  ctx.Repo.TreePath,
 				TreePath:      form.TreePath,
-				ContentReader: strings.NewReader(strings.ReplaceAll(form.Content, "\r", "")),
+				ContentReader: strings.NewReader(form.Content),
 			},
 		},
 		Signoff: form.Signoff,