Update docs & add example for #14221

[skip sauce]
Fixes #14213: Rouge 1.6.1
Fix #14224: Correctly document args passed to function vals for `title` & `content` options of tooltips+popovers
Fix #14219: Document that empty tooltips+popovers do not get displayed
Fix #14164: move Windows Phone 8 IE10 viewport bug workaround script to footer of pages
Merge pull request #14235 from twbs/doc-14221

Update docs & add example for #14221
Merge pull request #14258 from twbs/fix-14164

Move Windows Phone 8 IE10 viewport bug workaround script from head to footer
Merge pull request #14257 from twbs/fix-14219

Document that empty tooltips+popovers do not get displayed
Merge pull request #14256 from twbs/fix-14224

Correctly doc args passed to function vals for `title` & `content` options of tooltips+popovers
Document arguments passed to `placement` function of tooltip/popover

Closes #14255
Merge pull request #14264 from hnrch02/document-placement-args

Document arguments passed to `placement` function of tooltip/popover