CORS MW causes issues with Vary header.

[fishcakeday]

hono/src/middleware/cors/index.ts

Line 92 in fe7cfcf

set('Vary', 'Origin')

CORS middleware overrides Vary headers without checking for existing ones and causes a lot of issues with variable image types served based on Accept header. Please consider making it so it either merges into existing headers or leaves it alone if it is present.

[fzn0x]

Fixed in my PR, review are appreciated.