* Implement insertafter operator (like insertbefore)
Currently, the behavior of insertafter if the target is not found is to
append the inserted tiddler to the end of the list, like insertbefore
does. In the next commit, we'll add a suffix to customize what both
insertafter and insertbefore do when the target is not found.
* Add failing tests for insertafter suffixes
Also includes tests for insertbefore suffixes (start/end), since we'll
be implementing both of those at the same time.
* Add start/end suffixes for insertafter/before
The tests that exercise the start/end suffixes now pass.
* Add `main` and `article` roles to stories and story.
* Support `role` and \aria-checked` in buttons, and integrate with sidebar tabs.
* Add `region` role to sidebar, and set caption as `aria-label`.
* Add accessibility roles and labels to static templates.
* Update test fixtures with new ARIA tab attributes.
Global variables access within attributes will automatically trigger a refresh if the attribute text changes, but that wasn't happening for transclusions.
The objective is to add a $depth attribute so that it is possible to reach up to retrieve the parameters of ancestor transclusions. However, doing so requires changing the encoding of parameter names so that it is not possible for a user parameter to clash with an attribute like $depth. So now we have to double up dollars on any attribute names seen by the parameters widget, just like with the transclude widget itself.
Can invoke any functions, not just those start with a period. And can pass zero parameters (in contrast when invoked as a custom filter operator there's no way to omit the first parameter).
So far it appears to be totally backwards compatible... In practice, I think maybe this and the conversion of the other macros should go into a separate subsequent PR.
The basic idea is that if we don't find a variable `foo` then we fallback to retrieving the value from the tiddler `$:/global/foo`, if it exists.
This allows us to replace the usual importvariables-based mechanism for global definitions, avoiding cluttering up the variable namespace with every macro.
In order to permit subprocedures to be overridden, we also introduce a mechanism for conditional definitions: preceding the word definition|procedure|function|widget with a + causes the definition only to occur if the specified variable doesn't already exist. In the next commit we'll apply this mechanism to the tabs macro
