CI and README: yarn -> npm

.circleci/config.yml

@@ -2,14 +2,14 @@ version: 2
 jobs:
   build:
     docker:
-      - image: electronuserland/builder:16
+      - image: electronuserland/builder:18
     steps:
       - checkout
       - run:
           name: "Build"
           command: |
-            yarn install
-            yarn run electron:build
+            npm ci --legacy-peer-deps
+            npm run electron:build
 workflows:
   version: 2
   build_and_deploy:

README.md

@@ -20,17 +20,17 @@ Feedback, suggestions and contributions very much welcome! Please open an issue
 
 ## Develop
 
-Install git (if you haven't already) and [install Volta](https://docs.volta.sh/guide/getting-started) (which will make the correct Node.js and Yarn versions availlable in the project directory), then:
+Install git (if you haven't already) and [install Volta](https://docs.volta.sh/guide/getting-started) (which will make the correct Node.js and npm versions availlable in the project directory), then:
 
     git clone [email protected]:mb21/panwriter.git
     cd panwriter
-    yarn install
+    npm ci
 
     ## To run the app in development mode:
-    yarn run electron:dev
+    npm run electron:dev
 
     ## To build distributable app package (goes to ./dist):
-    yarn dist
+    npm dist
 
 Check out the `package.json` for more scripts to run.