Add Delicious import

Since 2021, you can export again your data \o/

Also fix indentation in json fixtures files.

tests/Wallabag/ImportBundle/fixtures/delicious_export.2021.02.06_21.10.json

@@ -0,0 +1,44 @@
+[
+  {
+    "title": "basket.js - a simple script loader that caches scripts with localStorage",
+    "tags": [
+      "basket",
+      "javascript",
+      "loader",
+      "localStorage"
+    ],
+    "url": "https://addyosmani.com/basket.js/",
+    "description": "\"A simple (proof-of-concept) script loader that caches scripts with localStorage\"",
+    "created": "1358531607",
+    "others": 9,
+    "owner": "maciej",
+    "private": "0"
+  },
+  {
+    "title": "Review - Stack Overflow",
+    "tags": [
+      ""
+    ],
+    "url": "https://stackoverflow.com/review/",
+    "description": "",
+    "created": "1358457437",
+    "others": 84,
+    "owner": "maciej",
+    "private": "0"
+  },
+  {
+    "title": "Announcing SpoofMAC - Spoof your MAC address in Mac OS X",
+    "tags": [
+      "MAC_address",
+      "osx",
+      "mac",
+      "spoof"
+    ],
+    "url": "https://feross.org/spoofmac/",
+    "description": "",
+    "created": "1358425796",
+    "others": 6,
+    "owner": "maciej",
+    "private": "0"
+  }
+]