Added icon for keygen.sh (#4925)

## Description
Added 2 new icons
keygen icon was taken directly from keygen.sh, LinkedIn icon is from
Wikipedia

## Tests

auth/assets/custom-icons/_data/custom-icons.json

@@ -492,6 +492,12 @@
     {
       "title": "Kagi"
     },
+    {
+      "title": "Keygen",
+      "altNames": [
+        "keygen.sh"
+      ]
+    },
     {
       "title": "Kick"
     },

auth/assets/custom-icons/icons/keygen.svg

@@ -0,0 +1,19 @@
+<svg width="100%" height="100%" viewBox="0 0 113 113" version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" xml:space="preserve" xmlns:serif="http://www.serif.com/" style="fill-rule:evenodd;clip-rule:evenodd;stroke-linejoin:round;stroke-miterlimit:2;">
+    <g transform="matrix(1,0,0,1,-1298.97,-1016.72)">
+        <g transform="matrix(0.5,0,0,0.5,736.463,641.721)">
+            <g transform="matrix(0.834925,0,0,0.834925,161.667,288.323)">
+                <circle cx="1198.72" cy="777.527" r="44.914" style="fill:#000811;"/>
+            </g>
+        </g>
+        <g transform="matrix(0.5,0,0,0.5,736.463,641.721)">
+            <g transform="matrix(0.834925,0,0,0.834925,311.66,138.323)">
+                <circle cx="1198.72" cy="777.527" r="44.914" style="fill:#000811;"/>
+            </g>
+        </g>
+        <g transform="matrix(0.5,0,0,0.5,736.463,641.721)">
+            <g transform="matrix(1,0,0,1,281.792,137.715)">
+                <path d="M955.708,762.285C935.011,762.285 918.208,745.482 918.208,724.785C918.208,704.088 935.011,687.285 955.708,687.285C976.405,687.285 993.208,704.088 993.208,724.785C993.208,745.482 1010.01,762.285 1030.71,762.285C1051.4,762.285 1068.21,779.088 1068.21,799.785C1068.21,820.482 1051.4,837.285 1030.71,837.285C1010.01,837.285 993.208,820.482 993.208,799.785C993.208,779.088 976.405,762.285 955.708,762.285Z" style="fill:#000811;"/>
+            </g>
+        </g>
+    </g>
+</svg>