Apply transition modifier local conditionally

[janosh]

Describe the problem

Is there a way to make transitions local conditionally?

Describe the proposed solution

Could become a transition param:

<h1 transition:fade={{ local: cond }}>Hello world!</h1>

Alternatives considered

Maybe this?

<h1 transition:fade|local:cond>Hello world!</h1>

Though that seems bad as people might then expect this to work:

<h1 transition:fade|local={cond}>Hello world!</h1>

which conflicts with current param passing mechanism.

REPL for testing if any of these already work.

Importance

nice to have

[dummdidumm]

Somewhat related to #6942