Reusable action for yarn setup + install.

Reduserer duplisering av kode i pipeline.

.github/actions/setup-install/action.yml

@@ -0,0 +1,23 @@
+name: Setup + Install
+description: Run commands needed to setup yarn and install dependencies.
+inputs:
+  npmAuthToken:
+    description: Token that has packages:read permission for the navikt organization
+    required: true
+
+runs:
+  using: composite
+  steps:
+    - uses: ../setup-yarnrc
+      with:
+        npmAuthToken: ${{ inputs.npmAuthToken }}
+
+    - name: Sette opp node
+      uses: actions/setup-node@v4
+      with:
+        node-version: '18'
+        cache: yarn
+
+    - name: Installere dependencies
+      shell: bash
+      run: HUSKY=0 yarn install --immutable

.github/workflows/lint-tscheck-build.yml

@@ -19,19 +19,11 @@ jobs:
       - name: Hente kode
         uses: actions/checkout@v4
 
-      - uses: ./.github/actions/setup-yarnrc
+      - name: Setup + install
+        uses: ./.github/actions/setup-install
         with:
           npmAuthToken: ${{ secrets.READER_TOKEN }}
 
-      - name: Sette opp Node
-        uses: actions/setup-node@v4
-        with:
-          node-version: '18'
-          cache: 'yarn'
-
-      - name: Installere dependencies
-        run: HUSKY=0 yarn install --immutable
-
       - name: Typescript-sjekk
         run: yarn ts-check