Running composer install fails without php-exif

[kesselb]

Regression from #3251

The php-exif is optional and was not installed in my docker container. While there's code handling the absence of php-exif gracefully, running composer fails because php-exif is a hard dependency for webp-exif.

It's probably fine to keep it like that and just require exif when working with a git checkout.
Moving webp-exif to suggested will likely not work without adjusting the build scripts.

Just noting it here to raise a bit of awareness.

Your lock file does not contain a compatible set of packages. Please run composer update.

  Problem 1
    - woltlab/webp-exif is locked to version v0.1.1 and an update of this package was not requested.
    - woltlab/webp-exif v0.1.1 requires ext-exif * -> it is missing from your system. Install or enable PHP's exif extension.

To enable extensions, verify that they are enabled in your .ini files:
    - /usr/local/etc/php/conf.d/custom.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-apcu.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-bcmath.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-excimer.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-ftp.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-gd.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-gmp.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-imagick.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-imap.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-intl.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-ldap.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-memprof.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-oci8.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-opcache.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-pcntl.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-pdo_mysql.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-pdo_pgsql.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-redis.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-smbclient.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-sodium.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-xdebug.ini
    - /usr/local/etc/php/conf.d/docker-php-ext-zip.ini
You can also run `php --ini` in a terminal to see which files are used by PHP in CLI mode.
Alternatively, you can run Composer with `--ignore-platform-req=ext-exif` to temporarily ignore these required extensions.