Add Lit icon and fix typo in the Contributions guidelines (#5571)

CONTRIBUTING.md

@@ -233,7 +233,7 @@ Icon metadata should be added to the `_data/simple-icons.json` file. Each icon i
 * A `hex` color value that matches the brand's primary color. All uppercase and without the `#` symbol.
 * The `source` URL of the logo being used. There are [more details below](#source-guidelines).
 
-The are also [optional values](#optional-data) that may be provided for each icon, which are listed below.
+There are also [optional values](#optional-data) that may be provided for each icon, which are listed below.
 
 Here is the object of a fictional brand as an example:
 

_data/simple-icons.json

@@ -4922,6 +4922,11 @@
             "hex": "ED3237",
             "source": "https://lionairthai.com/en/"
         },
+        {
+            "title": "Lit",
+            "hex": "324FFF",
+            "source": "https://github.com/lit/lit.dev/blob/5e59bdb00b7a261d6fdcd6a4ae529e17f6146ed3/packages/lit-dev-content/site/images/flame-favicon.svg"
+        },
         {
             "title": "Litecoin",
             "hex": "A6A9AA",

icons/lit.svg

@@ -0,0 +1 @@
+<svg role="img" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"><title>Lit icon</title><path d="M2.4 9.6l4.8 4.8V24l-4.8-4.8V9.6zm4.8-4.8v9.6L12 9.6V0L7.2 4.8zM12 9.6v9.6l4.8-4.8V4.8L12 9.6zm4.8 4.8V24l4.8-4.8V9.6l-4.8 4.8z"/></svg>