Add icon for R files (#8223)

Hugo Urías created 

Add an icon from https://www.svgrepo.com/svg/340612/logo-r-script for .r

<img width="1392" alt="307467014-63f68791-9d74-4bd1-8065-3698665f7c15"
src="https://github.com/zed-industries/zed/assets/93369643/ce24615c-6946-479a-8660-663bf83a7dde">

Credits For Image: @moshyfawn

Release Notes:

- Added R logo

Change summary

assets/icons/file_icons/file_types.json | 4 ++++
assets/icons/file_icons/r.svg           | 3 +++
2 files changed, 7 insertions(+)

Detailed changes

assets/icons/file_icons/file_types.json 🔗 

@@ -118,6 +118,7 @@
         "rebar.config": "erlang",
         "rkt": "code",
         "rs": "rust",
+        "r": "r",
         "rtf": "document",
         "sav": "storage",
         "scm": "code",
@@ -246,6 +247,9 @@
         "rust": {
             "icon": "icons/file_icons/rust.svg"
         },
+        "r": {
+            "icon": "icons/file_icons/r.svg"
+        },
         "settings": {
             "icon": "icons/file_icons/settings.svg"
         },

assets/icons/file_icons/r.svg 🔗 

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="15px" height="14px" viewBox="0 0 15 14" version="1.1">
+<g id="surface1">