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

lib/index.d.ts

@@ -91,12 +91,6 @@ declare namespace sharp {
         zlib?: string | undefined;
     };
 
-    /** An Object containing the platform and architecture of the current and installed vendored binaries. */
-    const vendor: {
-        current: string;
-        installed: string[];
-    };
-
     /** An Object containing the available interpolators and their proper values */
     const interpolators: Interpolators;