Improve subtitle rendering

src/assets/fonts/subtitles.css

src/assets/fonts/tiresias.css

src/assets/fonts/tiresias/Tiresias-Italic.ttf

src/assets/fonts/tiresias/Tiresias.ttf

src/index.tsx

src/routes/player/Player.tsx

src/util/subtitles/ttml/html.js

src/util/subtitles/ttml/styles.js