* [vcpkg docs] Change how documenting port functions works
Instead of using `##`, use comment blocks for documentation.
Also, add some minor docs and change RST -> MD
so we actually get docs generated.
* add CI stuff
* regenerate docs
* fix vcpkg_find_acquire_program to not use _execute_process
* [vcpkg_check_features] Set OUT_EXPAND_OPTIONS explicitly
* [vcpkg_check_features] Allow reverse logic for features
* [vcpkg_check_features] Document new parameters
* [vcpkg_check_features] Remove unnecessary logging
* Do not create variables for each feature only set OUT_FEATURE_OPTIONS
* Improve documentation
* Update ports that use vcpkg_check_features()
* Missing documentation updates
* [pcl] Fix tools feature
* [opencv,opencv4] Fix usage of vcpkg_check_features()
* [opencv4] Fix typo
Setting a variable in PARENT_SCOPE will not make the variable also visible in
current scope, which, as a result, causes FEATURE_OPTIONS to be set incorrectly.
