🔍️(frontend) add link to the source code in the footer

Great idea suggested by @fflorent — totally worth it!

src/frontend/src/layout/Footer.tsx

@@ -242,7 +242,7 @@ export const Footer = () => {
               {t('links.data')}
             </A>
           </StyledLi>
-          <StyledLi>
+          <StyledLi divider>
             <A
               externalIcon
               underline={false}
@@ -255,6 +255,17 @@ export const Footer = () => {
               {t('links.accessibility')}
             </A>
           </StyledLi>
+          <StyledLi>
+            <A
+              externalIcon
+              underline={false}
+              footer="minor"
+              href="https://github.com/numerique-gouv/meet/"
+              aria-label={t('links.code') + ' - ' + t('links.ariaLabel')}
+            >
+              {t('links.code')}
+            </A>
+          </StyledLi>
         </SecondRow>
         <ThirdRow>
           {t('mentions')}{' '}

src/frontend/src/locales/de/global.json

@@ -34,7 +34,8 @@
       "legalsTerms": "",
       "data": "",
       "accessibility": "",
-      "ariaLabel": ""
+      "ariaLabel": "",
+      "code": ""
     },
     "mentions": "",
     "license": ""

src/frontend/src/locales/en/global.json

@@ -34,7 +34,8 @@
       "legalsTerms": "Legal Notice",
       "data": "Personal Data and Cookies",
       "accessibility": "Accessibility: audit in progress",
-      "ariaLabel": "new window"
+      "ariaLabel": "new window",
+      "code": "Open Source Code Repository"
     },
     "mentions": "Unless otherwise stated, the contents of this site are available under",
     "license": "etalab 2.0 license"

src/frontend/src/locales/fr/global.json

@@ -34,7 +34,8 @@
       "legalsTerms": "Mentions légales",
       "data": "Données personnelles et cookie",
       "accessibility": "Accessibilités : audit en cours",
-      "ariaLabel": "nouvelle fenêtre"
+      "ariaLabel": "nouvelle fenêtre",
+      "code": "Dépôt de code Open Source"
     },
     "mentions": "Sauf mention contraire, les contenus de ce site sont disponibles sous",
     "license": "licence etalab 2.0"