[frontend] Better autocapitalize/spellcheck settings on forms (#3077)

web/template/sign-up.tmpl

@@ -58,6 +58,8 @@
                     required
                     placeholder="Please enter your desired username"
                     pattern="^[a-z0-9_]{1,64}$"
+                    autocapitalize="off"
+                    spellcheck="false"
                     title="lowercase a-z, numbers, and underscores; max 64 characters"
                 >
             </div>
@@ -75,6 +77,7 @@
                     rows="8"
                     minlength="40"
                     maxlength="500"
+                    autocapitalize="sentences"
                     title="40-500 characters"
                 ></textarea>
             </div>