This change swaps the CommonJS require() syntax in the Webpacker
application.js pack template file and in documentation examples with ES
module import syntax.

Benefits of this change include:

Provides continuity with the larger frontend community: Arguably, one of
the main draws in adopting Webpacker is its integration with Babel to
support ES module syntax. For a fresh Rails install with Webpacker, the
application.js file will be the first impression most Rails developers
have with webpack and Webpacker.  Most of the recent documentation and
examples they will find online for using other libraries will be based
on ES module syntax.

Reduces confusion: Developers commonly add ES imports to their
application.js pack, typically by following online examples, which means
mixing require() and import statements in a single file. This leads to
confusion and unnecessary friction about differences between require()
and import.

Embraces browser-friendliness: The ES module syntax forward-looking and
is meant to be supported in browsers. On the other hand, require()
syntax is synchronous by design and not browser-supported as CommonJS
originally was adopted in Node.js for server-side JavaScript. That
webpack supports require() syntax is merely a convenience.

Encourages best practices regarding optimization: webpack can statically
analyze ES modules and "tree-shake", i.e., strip out unused exports from
the final build (given certain conditions are met, including
`sideEffects: false` designation in package.json).

`a ActionDispatch::Http::UploadedFile object` ->
`an ActionDispatch::Http::UploadedFile object`

Don't upsize images smaller than the specified dimensions.

Fixes #33083

ImageProcessing gem is a wrapper around MiniMagick and ruby-vips, and
implements an interface for common image resizing and processing. This
is the canonical image processing gem recommended in [Shrine], and
that's where it developed from. The initial implementation was extracted
from Refile, which also implements on-the-fly transformations.

Some features that ImageProcessing gem adds on top of MiniMagick:

  * resizing macros
    - #resize_to_limit
    - #resize_to_fit
    - #resize_to_fill
    - #resize_and_pad
  * automatic orientation
  * automatic thumbnail sharpening
  * avoids the complex and inefficient MiniMagick::Image class
  * will use "magick" instead of "convert" on ImageMagick 7

However, the biggest feature of the ImageProcessing gem is that it has
an alternative implementation that uses libvips. Libvips is an
alternative to ImageMagick that can process images very rapidly (we've
seen up 10x faster than ImageMagick).

What's great is that the ImageProcessing gem provides the same interface
for both implementations. The macros are named the same, and the libvips
implementation does auto orientation and thumbnail sharpening as well;
only the operations/options specific to ImageMagick/libvips differ. The
integration provided by this PR should work for both implementations.

The plan is to introduce the ImageProcessing backend in Rails 6.0 as the
default backend and deprecate the MiniMagick backend, then in Rails 6.1
remove the MiniMagick backend.

* File.open("~/face.jpg") raise error:
  `Errno::ENOENT: No such file or directory @ rb_sysopen - ~/face.jpg`

* MessagesController redirects to `GET /message/:id`.
* It looks it don't expect XHR request.
* `form_with` behaves for XHR by default.
* I've added `local: true` option to `form_with`.

Active Storage was now merged to master and it is automatically
installed in a new application.

* Extend image_tag to accept ActiveStorage's Attachments and Variants

* Flip resolve_image_source around

* Add tests for the new use-cases of image_tag

* Remove the higher-level test

* Update image_tag documentation

* Add error states into the test suite

* Re-raise polymorhic_url's NoMethodError as ArgumentError

* delegate_missing_to will raise DelegationError instead of NoMethodError

changed `rails/activestorage` to `rails/rails`.

Omit azure-core (it's required by azure-storage), remove require:false to match other points.

previously https://github.com/rails/activestorage/pull/86