[Navigation]: Make it possible to set the icon via a slot

[fallaciousreasoning]

This will allow consumers to pass in custom icons (ie. an inline svg)

helps with #847

[github-actions]

👋 Thanks for Submitting! This PR is available for preview at the link below.

✅ PR tip preview: https://848.pr.nala.bravesoftware.com/
✅ Commit preview: https://848.pr.nala.bravesoftware.com/commit-4728b7af36b3928309a1c18df34b4caf5aee416b/

- ./tokens/css/variables-android.old.css: 7424 bytes
+ ./tokens/css/variables-android.css: 7424 bytes
---
- ./tokens/css/variables-browser.old.css: 6874 bytes
+ ./tokens/css/variables-browser.css: 6874 bytes
---
- ./tokens/css/variables-ios.old.css: 7067 bytes
+ ./tokens/css/variables-ios.css: 7067 bytes
---
- ./tokens/css/variables-marketing.old.css: 13561 bytes
+ ./tokens/css/variables-marketing.css: 13561 bytes
---
- ./tokens/css/variables-news.old.css: 526 bytes
+ ./tokens/css/variables-news.css: 526 bytes
---
- ./tokens/css/variables-newtab.old.css: 1941 bytes
+ ./tokens/css/variables-newtab.css: 1941 bytes
---
- ./tokens/css/variables-search.old.css: 2419 bytes
+ ./tokens/css/variables-search.css: 2419 bytes
---
- ./tokens/css/variables-web3.old.css: 905 bytes
+ ./tokens/css/variables-web3.css: 905 bytes
---
- ./tokens/css/variables.old.css: 114834 bytes
+ ./tokens/css/variables.css: 114834 bytes

Variables Diff: variables-android.diff

--- ./tokens/css/variables-android.old.css	2024-10-02 00:08:13.515347276 +0000
+++ ./tokens/css/variables-android.css	2024-10-02 00:07:35.470527091 +0000
@@ -1,6 +1,6 @@
 /**
  * Do not edit directly
- * Generated on Sun Sep 29 2024 19:55:24 GMT+0000 (Coordinated Universal Time)
+ * Generated on Wed Oct 02 2024 00:07:35 GMT+0000 (Coordinated Universal Time)
  */
 
 :root {

Variables Diff: variables-browser.diff

--- ./tokens/css/variables-browser.old.css	2024-10-02 00:08:13.907345396 +0000
+++ ./tokens/css/variables-browser.css	2024-10-02 00:07:35.455527158 +0000
@@ -1,6 +1,6 @@
 /**
  * Do not edit directly
- * Generated on Sun Sep 29 2024 19:55:24 GMT+0000 (Coordinated Universal Time)
+ * Generated on Wed Oct 02 2024 00:07:35 GMT+0000 (Coordinated Universal Time)
  */
 
 :root {

Variables Diff: variables-ios.diff

--- ./tokens/css/variables-ios.old.css	2024-10-02 00:08:14.315343442 +0000
+++ ./tokens/css/variables-ios.css	2024-10-02 00:07:35.488527009 +0000
@@ -1,6 +1,6 @@
 /**
  * Do not edit directly
- * Generated on Sun Sep 29 2024 19:55:24 GMT+0000 (Coordinated Universal Time)
+ * Generated on Wed Oct 02 2024 00:07:35 GMT+0000 (Coordinated Universal Time)
  */
 
 :root {

Variables Diff: variables-marketing.diff

--- ./tokens/css/variables-marketing.old.css	2024-10-02 00:08:14.677341707 +0000
+++ ./tokens/css/variables-marketing.css	2024-10-02 00:07:35.521526860 +0000
@@ -1,6 +1,6 @@
 /**
  * Do not edit directly
- * Generated on Sun Sep 29 2024 19:55:24 GMT+0000 (Coordinated Universal Time)
+ * Generated on Wed Oct 02 2024 00:07:35 GMT+0000 (Coordinated Universal Time)
  */
 
 :root {

Variables Diff: variables-news.diff

--- ./tokens/css/variables-news.old.css	2024-10-02 00:08:14.883340717 +0000
+++ ./tokens/css/variables-news.css	2024-10-02 00:07:35.546526747 +0000
@@ -1,6 +1,6 @@
 /**
  * Do not edit directly
- * Generated on Sun Sep 29 2024 19:55:24 GMT+0000 (Coordinated Universal Time)
+ * Generated on Wed Oct 02 2024 00:07:35 GMT+0000 (Coordinated Universal Time)
  */
 
 :root {

Variables Diff: variables-newtab.diff

--- ./tokens/css/variables-newtab.old.css	2024-10-02 00:08:15.238339053 +0000
+++ ./tokens/css/variables-newtab.css	2024-10-02 00:07:35.555526707 +0000
@@ -1,6 +1,6 @@
 /**
  * Do not edit directly
- * Generated on Sun Sep 29 2024 19:55:24 GMT+0000 (Coordinated Universal Time)
+ * Generated on Wed Oct 02 2024 00:07:35 GMT+0000 (Coordinated Universal Time)
  */
 
 :root {

Variables Diff: variables-search.diff

--- ./tokens/css/variables-search.old.css	2024-10-02 00:08:15.595337382 +0000
+++ ./tokens/css/variables-search.css	2024-10-02 00:07:35.541526770 +0000
@@ -1,6 +1,6 @@
 /**
  * Do not edit directly
- * Generated on Sun Sep 29 2024 19:55:24 GMT+0000 (Coordinated Universal Time)
+ * Generated on Wed Oct 02 2024 00:07:35 GMT+0000 (Coordinated Universal Time)
  */
 
 :root {

Variables Diff: variables-web3.diff

--- ./tokens/css/variables-web3.old.css	2024-10-02 00:08:16.032335338 +0000
+++ ./tokens/css/variables-web3.css	2024-10-02 00:07:35.561526680 +0000
@@ -1,6 +1,6 @@
 /**
  * Do not edit directly
- * Generated on Sun Sep 29 2024 19:55:24 GMT+0000 (Coordinated Universal Time)
+ * Generated on Wed Oct 02 2024 00:07:35 GMT+0000 (Coordinated Universal Time)
  */
 
 @media (prefers-color-scheme: light) {

Variables Diff: variables.diff

--- ./tokens/css/variables.old.css	2024-10-02 00:08:16.913331214 +0000
+++ ./tokens/css/variables.css	2024-10-02 00:07:35.313527800 +0000
@@ -1,6 +1,6 @@
 /**
  * Do not edit directly
- * Generated on Sun Sep 29 2024 19:55:24 GMT+0000 (Coordinated Universal Time)
+ * Generated on Wed Oct 02 2024 00:07:35 GMT+0000 (Coordinated Universal Time)
  */
 
 :root {