Xwidget and other modules

[A6GibKm]

I regularly need a clean Emacs build to test stuff and compare to behaviours with other Emacs branches or forks, it would be nice to have xwidgets for example, see #13.

I can make such a PR if there is any interest on this @muep . Same applies to flags as --with-modules, --with-jansson (required for new json native parser in Emacs 27), harfbuzz (Also introduced in Emacs 27), --with-cairo, --with-gtk3, etc. Which are some of the most popular flags.

Of course each of these features would be on its own PR and priority would be for xwidgets and the features added in emacs 27.

[muep]

@A6GibKm sorry for the long response. I am now finding more time to pay attention to this flatpak. This means that at least I am more open to having a small number of libraries bundled. Jansson seems to already be arriving in #36.

My impression is that for most of these optional features, we seem to require bundling of deps - simply adding a flag will not work since Emacs configure step would typically automatically enable all the features whose requirements are satisfied.

Feel free to submit PRs, though I also have plans to check through the issues this weekend. For each added dependency, I think we should assess the benefit/risk a bit. For the Jansson PR it seems that a single trivially building dependency suffices, and it seems to be a pretty mature library, rarely requiring urgent patching. I suppose that bundling a webkitgtk will be more exciting.