Suggest installing Bootstrap assets via composer

[mehov]

FriendsOfCake/bootstrap-ui does not come with Bootstrap itself, so we need to install the whole thing separately.

Right now the recommended way to do that seems to be via npm, either using bin/cake bootstrap install or manually:

• README.md#using-the-bootstrap-commands
• README.md#installing-bootstrap-assets-via-npm

Consider recommending getting Bootstrap from composer. I think that's much faster, more native to PHP and does not require npm to be available.

composer require twbs/bootstrap:5.3.3
composer require twbs/bootstrap-icons

(I had to install twbs/bootstrap-icons separately because twbs/bootstrap doesn't seem to contain the font directory.)

Link your application webroot to where Bootstrap files are actually located:

mkdir ./webroot/bootstrap_u_i
ln -s ../../vendor/twbs/bootstrap/dist/css ./webroot/bootstrap_u_i/css
ln -s ../../vendor/twbs/bootstrap/dist/js ./webroot/bootstrap_u_i/js
ln -s ../../vendor/twbs/bootstrap-icons/font ./webroot/bootstrap_u_i/font

The default FriendsOfCake/bootstrap-ui layout expects the files to be available under /bootstrap_u_i, so by symlinking the path like that, it picks almost everything up right away automatically.

[mehov]

Only /bootstrap_u_i/js/popper.js didn't get picked up automatically because it never gets compiled like I assume it would under npm.

[umer936]

I would prefer to have Bootstrap included using composer instead of npm as well.

The ./webroot/bootstrap_u_i folder should be created by bin/cake plugin assets symlink, but maybe the other symlinks could be done in the InstallCommand.php