Add a basic form containing the wally captcha

According to #9, It would be nice to have an administration interface allowing to add a new "Where's Wally" image.

When added, it will split automatically via a doctrine event.

Check if image already split, and do it if not.

Make it responsive and improve a little the design

Add admin page to select valid image (maybe, easyadmin if yes)

The default image when splitted generate images from 250 by 250 and the left width/height for the lasts splitted images are filled with black color which is not good
I recommend to give cols/rows parameters to split() function and generate splitted images based on these variables and source image width/height

As long as the valid image is not selected, block form submissions

Build assets before deployment in Github Actions (npm run build after npm ci)

The splitted images that are generated are not destroyed so if I want to split the same image with less cols/rows i'll have a duplicate image

Maybe can be good to have a "splitted" folder or something else to store generated images, and refresh it before each generation

Ref to #4, it would be cool not to generate the split at each refresh but only once with a command

Add a database (SQL/noSQL (sqlite or mongo ?), don't know) to store captcha information simply:

• Base image name
• List of generated images
• Name of the image containing Wally (the valid image)

The valid image will have to be selected manually, via an admin interface? (maybe)