add invalid query comment error message

[utamori]

It seems that the almost error handling is done.
but the following two typo cases error handling are missing in this.

• without a space after --
  • --name: {queryname} :{cmd}
• without : after name
  • -- name {queryname} :{cmd}

https://github.com/kyleconroy/sqlc/blob/master/internal/metadata/meta.go

Originally posted by @uta-mori in #836 (comment)