Hi,

In the text below, move point to the second half of the URL and
execute M-x browse-url-at-point.

```
[![Emacs](
https://www.gnu.org/software/emacs/images/emacs.png)](https://www.gnu.org/software/emacs/download.html
)
```

Firefox and Chromium-based browsers appear to open the URL "https//
www.gnu.org/software/emacs/download.html".
It seems that the ":" following https is deleted, but the browser actually
normalizes
the URL with the duplicate scheme "http://https://".

You can check this by executing M-: (browse-url-url-at-point).

Because thing-at-point-bounds-of-url-at-point function cannot correctly
recognize
URL bounds in the text.

I considered changing the thing-at-point-bounds-of-url-at-point algorithm,
but it would be a pain to change it without negatively impacting the
current behavior.
Ideally, thing-at-point-bounds-of-url-at-point will be fixed eventually,
but for now, the attached patch should easily fix the problem.