Various optimisations, now spreadsheets are loaded asynchronously.

+ adding stackoverflow icon
+ adding omegicons fontellico config.json for easier building next time.

i18n/en.json

@@ -62,6 +62,15 @@
     "file": {
         "other": "File:"
     },
+    "storeFlathub": {
+        "other": "Download on Flathub"
+    },
+    "storeSnapcraft": {
+        "other": "Get it from the Snap Store"
+    },
+    "storeFirefoxAddons": {
+        "other": "Get it from the Firefox Addons"
+    },
     "websiteSource": {
         "other": "Website source code"
     },

i18n/fr.json

@@ -62,6 +62,15 @@
     "file": {
         "other": "Fichier :"
     },
+    "storeFlathub": {
+        "other": "Installer depuis Flathub"
+    },
+    "storeSnapcraft": {
+        "other": "Installer à partir du Snap Store"
+    },
+    "storeFirefoxAddons": {
+        "other": "Installer depuis Firefox Addons"
+    },
     "websiteSource": {
         "other": "Code source du site"
     },