feat: rich embed for Spotify links and iframes

README.md

src/renderers/default/DefaultRenderer.test.ts

src/renderers/default/DefaultRenderer.ts

src/renderers/default/Localization.ts

src/renderers/default/StaticConfig.ts

src/renderers/default/embedder/AssetEmbedder.ts

src/renderers/default/embedder/HtmlDOMParser.ts

src/renderers/default/embedder/embedders/AbstractEmbedder.ts

src/renderers/default/embedder/embedders/Embedders.ts

...derers/default/embedder/embedders/SpotifyEmbedder.test.ts

src/renderers/default/embedder/embedders/SpotifyEmbedder.ts

src/renderers/default/embedder/embedders/TwitchEmbedder.ts

src/renderers/default/embedder/embedders/VimeoEmbedder.ts

src/renderers/default/embedder/embedders/YoutubeEmbedder.ts

...erers/default/embedder/utils/AccountNameValidator.test.ts

src/renderers/default/embedder/utils/AccountNameValidator.ts

...enderers/default/sanitization/TagTransformingSanitizer.ts