fix(node): Use node 16 everywhere (#400)

Author: UnstoppableMango

.github/workflows/pr.yml

@@ -13,7 +13,7 @@ jobs:
     - name: setup
       uses: actions/setup-node@v2
       with:
-        node-version: '15'
+        node-version-file: '.nvmrc'
     - name: install
       run: npm ci
     - name: test

.github/workflows/publish.yml

@@ -15,7 +15,7 @@ jobs:
     - name: setup-node
       uses: actions/setup-node@v2
       with:
-        node-version: '15'
+        node-version-file: '.nvmrc'
     - name: install
       run: npm ci
     - name: test

.nvmrc

@@ -1 +1 @@
-node
+16