fix: improve documentation hero on mobile

[mikaello]

Summary

• replace the marketing headline with the library name
• identify the package explicitly as ReScript bindings for @ctrl/tinycolor
• prevent API signatures and grid tracks from widening the document beyond the mobile viewport
• preserve consistent horizontal page padding at narrow widths

Testing

• npm run docs:build
• npm run check
• npm test (220 tests)
• responsive browser checks at 390px and 250px widths
• verified document scroll width exactly matches the viewport at both sizes