Add hreflang and x-default links where appropriate

[davidu1975]

Add hreflang and x-default links where appropriate

Workflow

• Ticket exists in Jira https://uktrade.atlassian.net/browse/GREATUK-1170
• Jira ticket has the correct status.
• A clear/description pull request messaged added.

Housekeeping

• Python requirements have been re-compiled.

Merging

• This PR can be merged by reviewers. (If unticked, please leave for the author to merge)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.76%. Comparing base (0a9e208) to head (87f1773).
Report is 6 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1066      +/-   ##
===========================================
+ Coverage    98.75%   98.76%   +0.01%     
===========================================
  Files           44       44              
  Lines         1929     1947      +18     
===========================================
+ Hits          1905     1923      +18     
  Misses          24       24              

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