Distribute prebuilt binaries via the npm registry #3750

- Remove all custom download logic for prebuilt binaries
- Add scripts to populate package contents
- Specify minimum versions of common package managers
- Remove sharp.vendor runtime API as no-longer relevant
- Update installation docs and issue templates

.github/workflows/ci.yml

@@ -37,6 +37,7 @@ jobs:
           - os: macos-11
             nodejs_arch: x64
             nodejs_version: "^18.17.0"
+            nodejs_version_major: 18
             platform: darwin-x64
             prebuild: true
           - os: macos-11
@@ -98,13 +99,17 @@ jobs:
           architecture: ${{ matrix.nodejs_arch }}
       - name: Checkout
         uses: actions/checkout@v4
-      - name: Fix working directory ownership
-        if: matrix.container
-        run: chown root.root .
       - name: Install
         run: npm install --build-from-source
       - name: Test
         run: npm test
+      - name: Test packaging
+        run: |
+          npm run package-from-local-build
+          npm pkg set "optionalDependencies.@sharpen/sharp-${{ matrix.platform }}=file:./npm/${{ matrix.platform }}"
+          npm run clean
+          npm install --ignore-scripts
+          npm test
       - name: Prebuild
         if: matrix.prebuild && startsWith(github.ref, 'refs/tags/')
         env:
@@ -130,9 +135,13 @@ jobs:
             mkdir /opt/nodejs
             curl --silent https://unofficial-builds.nodejs.org/download/release/v${nodejs_version}/node-v${nodejs_version}-linux-armv6l.tar.xz | tar xJC /opt/nodejs --strip-components=1
             export PATH=$PATH:/opt/nodejs/bin
-            chown root.root .
             npm install --build-from-source
             npx mocha --no-config --spec=test/unit/io.js
+            npm run package-from-local-build
+            npm pkg set "optionalDependencies.@sharpen/sharp-linux-arm=file:./npm/linux-arm"
+            npm run clean
+            npm install --ignore-scripts
+            npx mocha --no-config --spec=test/unit/io.js
             [[ -n $prebuild_upload ]] && npx prebuild || true
   macstadium-runner:
     permissions:
@@ -167,6 +176,13 @@ jobs:
         run: npm install --build-from-source
       - name: Test
         run: npm test
+      - name: Test packaging
+        run: |
+          npm run package-from-local-build
+          npm pkg set "optionalDependencies.@sharpen/sharp-${{ matrix.platform }}=file:./npm/${{ matrix.platform }}"
+          npm run clean
+          npm install --ignore-scripts
+          npm test
       - name: Prebuild
         if: matrix.prebuild && startsWith(github.ref, 'refs/tags/')
         env: