Hints for appcenter in testing

Hints

• asv-summary-has-dot-suffix
  :140 - Hwehwɛ dwumadie a wopɛ.
  The component summary should not end with a dot (`.`).
• asv-url-not-secure
  :254 - http://elementary.io/
  Consider using a secure (HTTPS) URL for this web link.
• asv-unknown-tag
  :259 - developer
  Found invalid tag. Non-standard tags should be prefixed with `x-`. AppStream also provides the <custom/> tag to add arbitrary custom data to metainfo files. This tag is read by AppStream libraries and may be useful instead of defining new custom toplevel or `x-`-prefixed tags if you just want to add custom data to a metainfo file.