Improve regex for financial variables check (#4156)

* Improves the regex for financial variables check to look for html entities and codes as well as characters

* Added minimum salary variable to salaries-banner

app/views/content/home/_salaries-banner.html.erb

@@ -1,6 +1,6 @@
 <div id="salary-banner" class="banner">
   <%= render CallsToAction::SimpleComponent.new(icon: "icon-money") do %>
-    <h2 class="call-to-action__heading">Earn a minimum of &pound;30k a year</h2>
+    <h2 class="call-to-action__heading">Earn a minimum of <%= v :salaries_starting_minshortened %> a year</h2>
     <p>All qualified teachers get a <strong>minimum starting salary of <%= v :salaries_starting_minshortened %></strong> (or higher in London), so it pays to do what you love.</p>
     <p>And with lots of opportunities to progress, you could <strong>earn over <%= v :salaries_fiveyears_maxshortened %> within 5 years</strong>.</p>
     <p><%= link_to("Find out more about teacher pay", page_path("life-as-a-teacher/pay-and-benefits/teacher-pay")) %>.</p>

spec/support/page_testing_support.rb

@@ -111,5 +111,5 @@ def build_url(host, link)
 end
 
 class MonetaryChecker
-  MONEY_REGEXP = /([$£€]\d+(,\d{3})*([.,]\d{1,2}p?)?k?)/m
+  MONEY_REGEXP = /(([$£€]|$|£|€|$|£|€)\d+(,\d{3})*([.,]\d{1,2}p?)?k?)/m
 end