Issue #3041699 by kjay, shaal, markconroy: Add the language switcher block to Umami Demo

...emo_umami/config/install/block.block.languageswitcher.yml

...o_umami/config/install/block.block.umami_account_menu.yml

...es/demo_umami/config/install/block.block.umami_search.yml

...components/blocks/language-switcher/language-switcher.css

...mami/themes/umami/css/components/blocks/search/search.css

...i/css/components/navigation/menu-account/menu-account.css

core/profiles/demo_umami/themes/umami/umami.libraries.yml