README: add sparse-encoder tag so the Hub widget shows the SparseEncoder snippet

README: library_name -> sentence-transformers; human-readable tokens in decode snippet

README: add Demo link to header + fold Space demo credit into the variant note (single blockquote)

Rewrite the README very slightly

Integrate with Sentence Transformers

Make LICENSE reference a clickable link

Add Apache-2.0 LICENSE (matches github.com/naver/v-splade)

V-SPLADE initial release