Normalize vendors.yaml, and don't spell-check it

[chalin]

• The Vendors data file doesn't contain any descriptions. I see little value in running spell-check over it, so I've added the data file name to the sSpell ignore paths list.
• Normalizes the vendors.yaml entries -- dropping unnecessary quotes.

There is no change in generated site files (other than the site timestamp):

$ (cd public && git diff -bw --ignore-blank-lines) | grep ^diff
diff --git a/site/index.html b/site/index.html