…weight but linking to translations if available

feat: if language switch shows language codes (instead of full language name), those codes are now uppercase
feat: translation list in post headers are replaced by links to translations in page headers - the old translation list in the post header can still be enabled using the boolean parameter "showTranslationListInPosts" (i.e. to turn it back on, add the parameter to your hugo.toml and set it to true)