Bug 1806793 - en-US dictionary: use .txt extensions for 5-mozilla-* files, convert to utf-8 encoding, r=sylvestre

5-mozilla-* files are a by-product of the dictionary generation, they're not used to generate the dictionaries, so we can safely use utf-8 encoding.

Also, since they are wordlists, it makes sense to use the TXT extensions.

Differential Revision: https://phabricator.services.mozilla.com/D165302

extensions/spellcheck/locales/en-US/hunspell/dictionary-sources/5-mozilla-added.txt

@@ -5946,14 +5946,14 @@ namespace's
 namespaces
 nano
 natively
-naďve
-naďvely
-naďver
-naďvest
-naďvety
-naďvety's
-naďveté
-naďveté's
+naïve
+naïvely
+naïver
+naïvest
+naïvety
+naïvety's
+naïveté
+naïveté's
 neato
 neoadjuvant
 neurocysticercoses