Add thesaurus search engine to qutebrowser

opening `t [searchterm]` in qutebrowser will go to thesaurus and look up
the corresponding term there.

qutebrowser/.config/qutebrowser/config.py

@@ -147,6 +147,7 @@ config.bind(leader + "VV", "config-source")
 c.url.searchengines = {
     "DEFAULT": "https://duckduckgo.com/?q={}",
     "d": "https://www.dict.cc/?s={}",
+    "t": "https://www.thesaurus.com/browse/{}",
     "gt": "https://translate.google.com/#auto/de/{}",
     "dt": "https://www.deepl.com/translator#en/de/{}",
     "g": "https://www.google.com/search?q={}",