code hinting support for CSS Regions and Exclusions

Adding code hinting support for these css region/exclusion properties
* flow-into
* flow-from
* region-break-after
* region-break-before
* region-break-inside
* region-fragment
* shape-inside
* shape-outside

Provided with this PR is change to position the cursor between parens for css value functions, e.g. shape-inside: circle(). This is a generalized implementation for cursor positioning and not specific to css regions/exclusions.