add example.

[ytetsuro]

Create an example directory in the project root and create a simple example that uses this library.

The sample meets the following requirements.

• Drag and drop images to upload them.
• Output the value of the uploaded dhash as a string to DOM.
• Allow the example code to be built with esbuild. (call esbuild by npx.)
• The web server will document how to set up the server so that it can be validated by the built-in server, such as php -S or python -m or npx http-server.

[silltho]

I would like to work on this.

Since this lib is written in Typescript should there be a runnable example (webpack + local server) or is it enough to just provide an uncompiled .ts file.

[ytetsuro]

@silltho

I don't need webpack + local server.

Also, you don't need the source code after the build.

I've also added a specification because the specification is unclear.