[Feature request] Auto-select prompt dialog text

For better usability (in at least certain contexts, e.g. for \), prompt dialog text should be auto-selected when the dialog is opened.


This feature was also requested by someone in #414, but that's a collection of several requests and this particular one doesn't seem to have gotten traction.

I had a quick look in the ComfyUI code, and a kludge fix could be done by adding `requestAnimationFrame(()=>dialog.querySelector("input")?.select?.());` to `LGraphCanvas.prototype.prompt()` in litegraph.core.js. But I'm not familiar at all with the codebase and don't know the potential corner cases.