Search for Flatpak binaries and ungoogled-chromium

[dawidpotocki]

No description provided.

[ZekeLu]

Thanks for the pull request! But in my opinion, those paths don't have to go into the lib. The users can specify a path that is not built-in easily:

	opts := append(chromedp.DefaultExecAllocatorOptions[:],
		chromedp.ExecPath("path to the browser"),
	)
	allocCtx, cancel := chromedp.NewExecAllocator(context.Background(), opts...)
	defer cancel()
	ctx, cancel := chromedp.NewContext(allocCtx)
	defer cancel()

[dawidpotocki]

Well, I saw that snap is included, so why not Flatpak?
Unlike snap it's not used only by Ubuntu.

I'm fine with taking out ungoogled-chromium, but I feel like Flatpak makes sense.

[ZekeLu]

FYI, chrome is still on flathub-beta and not graduated yet: https://discourse.flathub.org/t/google-chrome-on-flathub-beta/634

I will leave the decision to @kenshaw .

[dawidpotocki]

Chrome just got promoted to Flathub stable.
(and yes, I knew it wasn't there when I created the PR)
https://www.flathub.org/apps/details/com.google.Chrome
https://www.flathub.org/apps/details/com.google.ChromeDev