Fix typo in test 'it'

Author: szuend

src/encode/encode.test.ts

@@ -64,7 +64,7 @@ describe("encode", () => {
     assertThrows(() => encode(info));
   });
 
-  it("throws when a child range' start is not nested propertly within its parent", () => {
+  it("throws when a child range' start is not nested properly within its parent", () => {
     const info = builder.startRange(10, 0).startRange(0, 0).endRange(20, 0)
       .endRange(30, 0).build();