Add share custom filters option

We want to proactively improve the quality of filter lists. Therefore we could provide users with an option to share manually added filters with eyeo.

For instance, we could add a checkbox for that to the Block Element dialog which would cause the following information to be submitted to the existing issue reporter backend when adding a new filter using this dialog.

• Filter text
• Active filter lists
• Anonymized web page URL
• Extension, browser and platform info

See https://issues.adblockplus.org/ticket/2565 for further details

Implementation note: We may need to make this agnostic of where a custom filter is added from since this could also occur in the context of the options page. Therefore this may require adding a similar checkbox to the options page as well.