Adding Joplin icon (#6341)

Adding Joplin icon with a very high degree of precision.

_data/simple-icons.json

@@ -4660,6 +4660,11 @@
             "source": "https://docs.joomla.org/Joomla:Brand_Identity_Elements/Official_Logo",
             "guidelines": "https://docs.joomla.org/Joomla:Brand_Identity_Elements"
         },
+        {
+            "title": "Joplin",
+            "hex": "1071D3",
+            "source": "https://github.com/laurent22/joplin/blob/45e35576bd8b1bb0ffe958309cc1ab3736cc266b/Assets/JoplinLetter.svg"
+        },
         {
             "title": "Jordan",
             "hex": "000000",

icons/joplin.svg

@@ -0,0 +1 @@
+<svg role="img" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Joplin</title><path d="m20.969 0h-8.904c-.084 0-.152.068-.152.152v2.827c0 .095.077.172.172.172h1.221c.493 0 .894.38.937.863v13.378h-.001l-.017.363-.05.282c-.011.044-.02.089-.033.132-.081.258-.208.497-.384.708-.007.007-.015.014-.021.021-.054.063-.11.123-.172.18-.063.057-.13.11-.2.16-.498.353-1.169.508-1.918.436-.955-.089-1.903-.523-2.669-1.22-.765-.696-1.242-1.558-1.34-2.427-.089-.778.144-1.462.655-1.927.002-.001.003-.002.004-.003.02-.018.041-.033.062-.05.366-.307.842-.493 1.387-.544.006 0 .012-.001.017-.002l.298-.014.35.017c.008 0 .016.002.024.003.499.05.993.199 1.462.425.01 0 .022.003.036.011.143.079.17-.005.174-.061v-4.256c0-.122-.085-.23-.203-.256-2.527-.556-5.005.022-6.754 1.615-1.528 1.389-2.267 3.395-2.027 5.502.213 1.876 1.176 3.679 2.712 5.076 1.497 1.362 3.402 2.213 5.368 2.399.271.025.543.038.809.038 1.877 0 3.619-.644 4.905-1.814 1.218-1.109 1.948-2.632 2.055-4.288l.01-10.866h.001v-2.955c.011-.513.429-.926.945-.926h1.221c.095 0 .172-.077.172-.172v-2.827c0-.084-.068-.152-.152-.152z"/></svg>