docs: correct pluralization and capitalization typos (#5282)
docs: correct pluralization and capitalization typos (#5282)

* Update projection.md

* Fix capitalization of Vega-Lite

vega/vega-lite,vega/vega-lite,uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite,uwdata/vega-lite,uwdata/vega-lite,vega/vega-lite,uwdata/vega-lite,vega/vega-lite