Improve the org-web-tools-archive-view

Hi, this is a great package for my personal workflow with websites and links. I made use of the `-archive-attach` to keep local copy of certain worthwhile online article/post. The `-archive-view` function works great. However, I recently started utilizing more Emacs and realize a lot of these html files can be read and rendered quite well with built-in `eww`. But, it seems that the `archive-view` function is hard-coded with `browse-url-default-browser` inside ' org-web-tools-archive-view' function. I couldn't figure out how to change so that `eww` is used instead of the platform `firefox` browser.

I read up a bit on this and decided to clone the repo. I change `browse-url-default-browser` to `browse-url` on that specific code line. This modification can allow me to easily use `eww` . In my org-mode config, i use `(setq browse-url-browser-function 'eww-browse-url)`. And I can now read the html files archived by org-web-tools with eww.

Since my usage with org-web-tools is limited to some features and I couldn't test much if the above change affects other functionality, I didn't bother pushing / pull request with this very small change. But I hope this is helpful and worth taking a look for improvement.