accept any psr/log version

Since this library only consumes loggers, but does not implement any
loggers, it's safe to accept all three versions of psr/log making the
library more compatible with different environments.

See also https://www.php-fig.org/blog/2019/10/upgrading-psr-interfaces/

Author: splitbrain

composer.json

@@ -19,7 +19,7 @@
     ],
     "require": {
         "php": ">=5.4",
-        "psr/log": "~1.0"
+        "psr/log": "^1.0 || ^2.0 || ^3.0"
     },
     "require-dev": {
         "phpunit/phpunit": "~8.5",