use npm instead of yarn (ProjectOpenSea#32)

* use npm

* Fix scripts

* Update workflow

Author: sunwrobert

.github/workflows/main.yaml

@@ -19,18 +19,18 @@ jobs:
         uses: actions/setup-node@v2
         with:
           node-version: "16.11.0"
-          cache: yarn
+          cache: npm
         env:
           NODE_AUTH_TOKEN: ${{ secrets.GH_PAT_TOKEN }}
 
       - name: Install dependencies
-        run: yarn install --immutable --ignore-scripts
+        run: npm install --ignore-scripts
 
       - name: Build
-        run: yarn build
+        run: npm run build
 
       - name: Run linters
-        run: yarn lint
+        run: npm run lint
 
   tests:
     runs-on: ubuntu-latest
@@ -41,15 +41,15 @@ jobs:
         uses: actions/setup-node@v2
         with:
           node-version: "16.11.0"
-          cache: yarn
+          cache: npm
         env:
           NODE_AUTH_TOKEN: ${{ secrets.GH_PAT_TOKEN }}
 
       - name: Install dependencies
-        run: yarn install --immutable --ignore-scripts
+        run: npm install --ignore-scripts
 
       - name: Build
-        run: yarn build
+        run: npm run build
 
       - name: Run tests
-        run: yarn test
+        run: npm run lint

CONTRIBUTING.md

@@ -4,16 +4,14 @@
 
 We recommend using [nvm](https://github.com/nvm-sh/nvm) to manage Node.js versions. Execute `nvm use`, if you have `nvm` installed.
 
-We currently use [yarn](https://yarnpkg.com/getting-started/install) to manage dependencies.
-
-Then, run `yarn` after `yarn` is installed
+Then, run `npm`
 
 ## Running tests
 
 To run the tests:
 
 ```
-yarn test
+npm run test
 ```
 
 The first run might fail due to typechain needing to compile. If so, just run the command again.