Add GraphList data structure.

[waynemwashuma]

Objective

Introduces a new weighted graph data structure called GraphList. It is internally implemented as an adjacency list, making it efficient for representing sparse graphs.
The following are also added to support the structure:

• GraphNode: Represents a node in the graph.
• GraphEdge: Represents a directed edge between two nodes.
• NodeId: Internal reference identifier for nodes.
• EdgeId: Internal reference identifier for edges.

The graph can do the following:

• Create and store nodes and edges.
• Query neighbour nodes for a given node.
• Retrieve edges originating from a given node.

Note

The current implementation does not provide methods for removing nodes or edges.
Only directed graphs are supported at the moment.Support for undirected graphs may be added in the future.

Solution

N/A

Showcase

const graph = new GraphList<number,undefined>()
const node1 = graph.addNode(3)
const node2 = graph.addNode(2)
const edge1 = graph.addEdge(node1,node2)

Migration guide

N/A

Checklist

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.