Add test for phylogram layout

tests/phylogram-layout.test.ts

+import Phylogram from "../src/scripts/layout/phylogram";
+import { RawPhyloTreeNode } from "../src/scripts/types";
+
+describe("Test layout", () => {
+  const data: RawPhyloTreeNode = {
+    "name": "root",
+    branchLength: 0,
+    nodes: {
+      r: 2,
+      fill: "green"
+    },
+    "children": [
+      {
+        "name": "child0",
+        branchLength: 0.5,
+        nodes: {
+          fill: "blue"
+        }
+      },
+      {
+        "name": "child1",
+        branchLength: 0.6,
+        nodes: {
+          r: 8,
+          fill: "red"
+        },
+        "children": [
+          {
+            "name": "child10",
+            branchLength: 0.4
+          },
+          {
+            "name": "child11",
+            branchLength: 0.1
+          }
+        ]
+      }
+    ]
+  };
+  const height = 900;
+  const width = 1000;
+  const phylogramLayout = Phylogram().size([height, width]);
+  const pointData = phylogramLayout(data);
+  const child0 = (pointData.children) ? pointData.children[0] : { y: false };
+  const child10 = pointData.leaves().reduce((acc, curr) => {
+    return (curr.data.name === "child10") ? curr : acc;
+  }, pointData)
+  test("Root node middle height", () => {
+    expect(pointData.x).toBe(405);
+  })
+
+  // Test X
+  if (child0) {
+    test("Child 0", () => {
+      expect(child0.y).toBe(500);
+    });
+  }
+
+  // Test y
+  test("child10", () => {
+    expect(child10.y).toBe(width);
+  })
+
+  //test nodes object
+  test("root", () => {
+    const nodes = pointData.data.nodes;
+    if (nodes) {
+      expect(nodes.r).toBe(2);
+    }
+  })
+})
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