Adds baseline status to html elements and attributes

[rviscomi]

Progress on microsoft/vscode-css-languageservice#427

Similar to #111, this adds baseline info to the generated HTML data to be shown in element and attribute hovercards

All changes:

• adds new baseline and browsers objects to all supported HTML elements, element-specific attributes, and global attributes, in the same format as the one used by the CSS data
• adds all missing (non-deprecated) elements
  • search
  • fencedframe
  • selectedcontent
• adds a few missing element-specific attributes
  • img[fetchpriority]
  • input[popovertarget]
  • input[popovertargetaction]
  • button[popovertarget]
  • button[popovertargetaction]
• adds all missing global attributes
  • autocorrect
  • autofocus
  • enterkeyhint
  • inert
  • nonce
  • popover
  • virtualkeyboardpolicy
  • I intentionally did NOT add anchor, which is non-standard
• adds descriptions and valueSets for elements and attributes as needed

The missing elements and attributes were kind of important to add because they tend to be newer features, and developers would benefit from having clearer browser support info for those in particular.

[aeschli]

👍 Thanks @rviscomi !