Add sliding window to algorithm tips page (#346)

add algorithm tip

Signed-off-by: Brandon <brandonaltermatt@gmail.com>

Author: brandonaltermatt

src/components/Tips/index.js

@@ -33,6 +33,7 @@ If must solve in-place then
 
 If asked for maximum/minimum subarray/subset/options then
 - Dynamic programming
+- Sliding window
 
 If asked for top/least K items then
 - Heap