Support short notation for boolean values (e.g. hx-boost instead of hx-boost="true")

[MiErnst]

According to the HTML specification for boolean attributes it should be possible to write for example hx-boost (data-hx-boost) instead of hx-boost="true" (data-hx-boost="true").

The presence of a boolean attribute on an element represents the true value, and the absence of the attribute represents the false value.

[MichaelWest22]

Proper boolean attributes are not supposed to have values of true or false and to always be used just as the existence of the attribute only according to the spec. And hx-boost by default uses inheritance in htmx so needs the false option to operate fully. So I assume it was a deliberate decision to avoid the use and confusion possible with treating it like a boolean attribute.

Hx-preserve is an interesting similar attribute but inheritance was not sensible here and this attribute seems to be implemented with boolean attribute support but it is still common to document it with the same explicit true value to keep things in htmx consistent. But because here there is only one option it was simpler to implement it as a boolean existence check only.