Add Readme for DFS

Author: khairalanam

L-A/0003 DFSGRaph/README.md

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+# 0003 DFSGraph ( L-A )
+
+## Problem
+
+Implement a JavaScript function that implements a depth-first search (DFS) algorithm to traverse a graph.
+
+## Test Case
+
+```javascript
+graph_edges = [
+  [1, 2],
+  [1, 3],
+  [2, 3],
+  [3, 4],
+  [2, 4],
+  [4, 6],
+  [5, 6],
+  [1, 6],
+];
+```
+
+## Solution
+
+```javascript
+const DFSGraphTraversal = (graph, start, visited = new Set()) => {
+  console.log(start);
+  visited.add(start);
+  for (let child = 0; child < graph[start].length; child++) {
+    if (visited.has(graph[start][child]) === false) {
+      DFSGraphTraversal(graph, graph[start][child], visited);
+    }
+  }
+};
+```
+
+## How it works
+
+- We first create the graph out of the given array of edges using an `Object`.
+- We then run the `DFSGraphTraversal` function to execute the depth first search.
+- In the function, we have three parameters; namely the `graph`, the `start` node and the `visited` set which is empty by default.
+- Firstly, we print the `start` node and then we add the node to the `visited` set.
+- We then run a for loop for the elements present in the `graph[start]` array.
+- If the current element is not present in the `visited` set, then recursively call the `DFSGraphTraversal` function with the same `graph` and `visited` set, but with the current element as the `start` node.
+- This function will run until all the nodes are visited in the `graph`.
+
+## References
+
+- [Youtube](https://youtu.be/IG1ABs6lVMw)
+
+## Problem Added By
+
+- [khairalanam](https://github.com/khairalanam)
+
+## Contributing
+
+Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.
+
+Please make sure to update tests as appropriate.