Review Mozilla 1948326: Add feature to generate search engine from HTML forms

🔍 Bugzilla Audit

Bugzilla: https://bugzilla.mozilla.org/show_bug.cgi?id=1948326

Description

Allows the user to add custom search engines. Either by entering the URL manually in "Settings > Search > Add", or using the context menu for a search input.

E.g. go to wiktionary.org and open the context menu for the search input. Selecting "Add Search Engine" will add a custom search engine with the URL https://www.wiktionary.org/search-redirect.php?family=wiktionary&search=%s&language=en&go=Go.

The risk is that the URL may be linkable to the user and could track their searches between sessions.

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