Add container to tooltip options

[andyexeter]

Fixes #17755 by adding the already documented container option for tooltips and popovers.

[andyexeter]

Looks like this is failing because an element is being passed as an option in one of the tests. The documentation states that the container option type should be a string or boolean. Should I update the test or update the docs/code so an element is accepted?

[andyexeter]

Should be noted here as well as in #17755 that the container option will only work for elements which are position: static - otherwise Tether moves the popover/tooltip into the body. Should I update the docs to mention this?

[mdo]

@bardiharborow @Johann-S Any chance one of y'all could review this? <3

[bardiharborow]

@mdo, I've made a few changes in 0ded703, including fixing the build error and switching to const to be compliant with the new linting rules.

[mdo]

Added in 87a0749.