Install madge NPM package and eliminate circular dependencies

.github/workflows/test.yml

@@ -41,9 +41,11 @@ jobs:
       - name: Install npm packages
         run: npm ci
       - name: Check formatting
-        run: npm run format:check
+        run: npm run check.format
       - name: Lint code
         run: npm run lint
+      - name: Check for circular imports
+        run: npm run check.imports
       - name: Run build
         run: npm run build
       - name: Run unit tests

README.md

@@ -103,6 +103,14 @@ npm run lint
 > That tells npm you want it to run the script named `lint`, defined in the `package.json` file.
 > At the time of this writing, that script runs `eslint src`.
 
+### Run circular import check
+
+Identify circular imports using the [`madge`](https://github.com/pahen/madge) package.
+
+```shell
+npm run check.imports
+```
+
 ### Run automated tests
 
 #### Unit tests
@@ -155,10 +163,10 @@ You can use it like this:
 
 ```shell
 # Check whether any files are not formatted.
-npx run format:check
+npm run check.format
 
 # Format all files.
-npx run format
+npm run format
 ```
 
 The `.prettierignore` file tells Prettier which files we want it to