docs(guides): add icons and sidebar badges to guide pages

apps/docs/content/guides/(3-techniques)/combinatorics.mdx

@@ -1,6 +1,9 @@
 ---
 title: "Combinatorics"
 list: "https://leetcode.com/problem-list/combinatorics/"
+icon: dices
+sidebar:
+  badge: '1'
 ---
 
 :::note

apps/docs/content/guides/(3-techniques)/counting.mdx

@@ -1,6 +1,9 @@
 ---
 title: "Counting"
 list: "https://leetcode.com/problem-list/counting/"
+icon: tally-5
+sidebar:
+  badge: '3'
 ---
 
 :::note

apps/docs/content/guides/(3-techniques)/design.mdx

@@ -1,6 +1,9 @@
 ---
 title: "Design"
 list: "https://leetcode.com/problem-list/design/"
+icon: pencil-ruler
+sidebar:
+  badge: '5'
 ---
 
 :::note

apps/docs/content/guides/(3-techniques)/geometry.mdx

@@ -1,6 +1,9 @@
 ---
 title: "Geometry"
 list: "https://leetcode.com/problem-list/geometry/"
+icon: shapes
+sidebar:
+  badge: '1'
 ---
 
 :::note

apps/docs/content/guides/(3-techniques)/math.mdx

@@ -1,6 +1,9 @@
 ---
 title: "Math"
 list: "https://leetcode.com/problem-list/math/"
+icon: calculator
+sidebar:
+  badge: '6'
 ---
 
 :::note