Add Zettlr icon (#7590)

* Add Zettlr icon

* modify Zettlr icon

* add guidelines

Co-authored-by: Sachin Raja <sachinraja2349@gmail.com>

_data/simple-icons.json

@@ -12355,6 +12355,12 @@
             "hex": "7BBB6E",
             "source": "https://zerply.com/about/resources"
         },
+        {
+            "title": "Zettlr",
+            "hex": "1CB27E",
+            "source": "https://www.zettlr.com/",
+            "guidelines": "https://www.zettlr.com/press"
+        },
         {
             "title": "Zhihu",
             "hex": "0084FF",

icons/zettlr.svg

@@ -0,0 +1 @@
+<svg role="img" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Zettlr</title><path d="M2.46.188C.335.57.023 2.534.022 4.295L.02 17.325c0 1.545-.224 3.96.723 5.28 1.201 1.673 3.567 1.355 5.365 1.351l8.31.03c1.61-.003 5.626.104 7.2-.23 2.115-.448 2.326-2.31 2.328-4.082l.01-13.634c.001-1.532.311-3.425-.68-4.71C22.021-.296 19.557.025 17.744.026L13.24.043c-1.614 0-9.195-.14-10.782.145m14.249 3.665c0 .528.185 1.466-.037 1.947-.11.239-.49.384-.703.518-.496.315-.961.676-1.418 1.044-1.477 1.185-3.034 2.818-3.428 4.74-.182.895-.164 1.988.59 2.626 1.21 1.023 3.035-.024 4.317.987 1.337 1.053 1.14 3.071.37 4.39-.184.316-.417.797-.75.982-.23.13-.598.064-.853.064h-1.85c.057-.37.35-.58.575-.862.374-.47.673-.984.668-1.6-.01-1.157-1.127-1.17-1.983-1.17-1.518 0-3.296-.216-4.073-1.724-1.337-2.595.33-5.731 2.105-7.633.695-.746 1.684-1.333 2.276-2.154h-4.07V3.853z"/></svg>