Feature/put serve behind feature flag (#455)

* Add build-time feature flag capabilities

* Toggle `bw serve` command with `serve` flag

* Run linter and prettier

spec/utils.spec.ts

@@ -0,0 +1,27 @@
+import { FlagName } from "../src/flags";
+import { CliUtils } from "../src/utils";
+describe("flagEnabled", () => {
+  it("is true if flag is null", () => {
+    process.env.FLAGS = JSON.stringify({ test: null });
+
+    expect(CliUtils.flagEnabled("test" as FlagName)).toBe(true);
+  });
+
+  it("is true if flag is undefined", () => {
+    process.env.FLAGS = JSON.stringify({});
+
+    expect(CliUtils.flagEnabled("test" as FlagName)).toBe(true);
+  });
+
+  it("is true if flag is true", () => {
+    process.env.FLAGS = JSON.stringify({ test: true });
+
+    expect(CliUtils.flagEnabled("test" as FlagName)).toBe(true);
+  });
+
+  it("is false if flag is false", () => {
+    process.env.FLAGS = JSON.stringify({ test: false });
+
+    expect(CliUtils.flagEnabled("test" as FlagName)).toBe(false);
+  });
+});