Fix two typos in doc/site/performance.markdown: change "rivalling" to "rivaling" in the paragraph about language implementation complexity, and change "carvinal" to "carnival" in the benchmarks section.
Create new doc/site/performance.markdown explaining Wren's position in the bytecode interpreter performance bucket and introducing NaN tagging for compact value storage. Also update doc/site/template.html to include a link to the new performance page in the "Other" navigation section.