Add Legal Notice page link to .env

Is your feature request related to a problem? Please describe

Add Legal Notice page link to .env

Describe the solution you'd like

Add to .env:

app.legalNoticeURL="https://YOUR_LEGAL_NOTICE_PAGE_URL/"

File	Translation
app/Language/en/Page.php	'legal_notice' => 'Legal Notice',
app/Language/fr/Page.php	'legal_notice' => 'Mentions Légales',

Link should be displayed next to Home, Credits and Map links.

Describe alternatives you've considered

/

Additional context

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