Replace set-output with environment files in CI

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

.github/workflows/main.yml

@@ -99,11 +99,11 @@ jobs:
         # the asterisk matching behaviour, not the literal string.
         run: |
           if [ "${GITHUB_EVENT_NAME}" == "pull_request" ]; then
-              echo ::set-output name=baseURL::/
+              echo "baseURL=/" >> "$GITHUB_OUTPUT"
           elif [[ "${GITHUB_REF}" == refs/tags/* ]]; then
-              echo ::set-output name=baseURL::"/${GITHUB_REF/refs\/tags\//}"
+              echo "baseURL=/${GITHUB_REF/refs\/tags\//}" >> "$GITHUB_OUTPUT"
           else
-              echo ::set-output name=baseURL::/unstable
+              echo "baseURL=/unstable" >> "$GITHUB_OUTPUT"
           fi
 
   build-openapi:

.github/workflows/netlify.yaml

@@ -32,7 +32,7 @@ jobs:
           pr_number=$(curl -H 'Authorization: Bearer ${{ secrets.GITHUB_TOKEN }}' "$pulls_uri" |
                jq -r '.[] | .number')
           echo "PR number: $pr_number"
-          echo "::set-output name=prnumber::$pr_number"
+          echo "prnumber=$pr_number" >> "$GITHUB_OUTPUT"
         
       - name: '📥 Download artifact'
         uses: dawidd6/action-download-artifact@268677152d06ba59fcec7a7f0b5d961b6ccd7e1e # v2.28.0