update readme

Author: zwfang

README.md

@@ -88,6 +88,7 @@ continually updating 😃.
 * [120. Triangle](src/0120_triangle/triangle.go)   *`array`*
 * [198. House Robber](src/0198_house_robber/house_robber.go)
 * [300. Longest Increasing Subsequence](src/0300_longest_increasing_subsequence/lis.go)
+* [304. Range Sum Query 2D - Immutable](src/304_Range_Sum_Query_2D/rsq.go)
 * [343. Integer Break](src/0343_integer_break/integer_break.go)   *`math`*
 * [376. Wiggle Subsequence](src/0376_wiggle_subsequence/wiggle_subsequence.go)   *`greedy;`*  *`dynamic programming`*
 * [416. Partition Equal Subset Sum](src/0416_partition_equal_subset_sum/partition_equal_subset_sum.go)  *`0-1 knapsack problem`*

src/README.md

@@ -84,6 +84,7 @@
 |0283|[Move Zeroes(solution1)](./0283_move_zeroes/move_zeroes.go) <br/>  [Move Zeroes(solution2)](./0283_move_zeroes/move_zeroes2.go)|Easy|*`array`*|
 |0300|[Longest Increasing Subsequence](./0300_longest_increasing_subsequence/lis.go)|Medium|*`dp`*|
 |0303|[303. Range Sum Query - Immutable](0303_range_sum_query/rsqim.go)|Easy||
+|0304|[304. Range Sum Query 2D - Immutable](304_Range_Sum_Query_2D/rsq.go)|Medium|*`dp`*|
 |0307|[307. Range Sum Query - Mutable](0307_Range_Sum_Query_Mutable/range_sum_query_mut.go)|Medium|*`segment tree`*|
 |0328|[328. Odd Even Linked List](0328_odd_even_linked_list/odd_even_linked_list.go)|Medium|*`singly linked list`*|
 |0343|[Integer Break](./0343_integer_break/integer_break.go)|Medium|*`recursion;`* *`memory search;`* *`dynamic programming`*|