Split org Propfile README to a new tab overview (#31373)

like user profile, add a new overviw tab to show profile READEME when it
is exist.

replace #31349 (another solution option)

example view:
![屏幕截图 2024-06-14
094116](https://github.com/go-gitea/gitea/assets/25342410/3303a1f2-ae02-48e0-9519-7fa11e65657f)
![屏幕截图 2024-06-14
094101](https://github.com/go-gitea/gitea/assets/25342410/7a4a5a48-dc2b-4ad4-b2a2-9ea4ab5d5808)

---------

Signed-off-by: a1012112796 <1012112796@qq.com>

routers/web/shared/user/header.go

@@ -162,3 +162,15 @@ func LoadHeaderCount(ctx *context.Context) error {
 
 	return nil
 }
+
+func RenderOrgHeader(ctx *context.Context) error {
+	if err := LoadHeaderCount(ctx); err != nil {
+		return err
+	}
+
+	_, _, profileReadmeBlob, profileClose := FindUserProfileReadme(ctx, ctx.Doer)
+	defer profileClose()
+	ctx.Data["HasProfileReadme"] = profileReadmeBlob != nil
+
+	return nil
+}