docs(docs): add new problem documentation pages and source selector component

apps/docs/content/(01-linear-structures)/monotonic-stack/901_online-stock-span.mdx

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+---
+title: '901. Online Stock Span'
+description: Design an algorithm that collects daily price quotes for some stock and returns the span of that stock's price for the current day
+icon: dot
+topics:
+  - { name: "Stack", slug: "stack" }
+  - { name: "Design", slug: "design" }
+  - { name: "Monotonic Stack", slug: "monotonic-stack" }
+  - { name: "Data Stream", slug: "data-stream" }
+issue: "https://github.com/prdlk/leetcode/issues/75"
+sidebar:
+  label: 'Online Stock Span'
+  badge: 'Medium'
+---
+
+### Example 1:
+- Input: ``
+- Output: ``
+- Explanation: Input ["StockSpanner", "next", "next", "next", "next", "next", "next", "next"] `[[]`, `[100]`, `[80]`, `[60]`, `[70]`, `[60]`, `[75]`, [85]] Output [null, `1`, `1`, `1`, `2`, `1`, `4`, 6] Explanation StockSpanner stockSpanner = new StockSpanner(); stockSpanner.next(100); // return `1` stockSpanner.next(80);  // return `1` stockSpanner.next(60);  // return `1` stockSpanner.next(70);  // return `2` stockSpanner.next(60);  // return `1` stockSpanner.next(75);  // return `4`, because the last `4` prices (including today's `price` of `75`) were less than or equal to today's `price`. stockSpanner.next(85);  // return `6`
+
+### Constraints:
+
+- `1 <= price <= 10^5`
+- At most 10^4 calls will be made to next.
+
+## Solution
+
+```py
+class StockSpanner:
+    def __init__(self):
+        self.stack = []
+
+    def next(self, price: int) -> int:
+        ans = 1
+        while self.stack and self.stack[-1][0] <= price:
+            ans += self.stack.pop()[1]
+
+        self.stack.append([price, ans])
+        return ans
+
+
+# Your StockSpanner object will be instantiated and called as such:
+# obj = StockSpanner()
+# param_1 = obj.next(price)
+```