Fix rule management

The `value` is modified later (with `splice`),
so rules are not immutable, `unsafe-inline` rules
are deleted, if request comes from firefox.

On every request, rules should be cloned.
Fix rule management

The `value` is modified later (with `splice`),
so rules are not immutable, `unsafe-inline` rules
are deleted, if request comes from firefox.

On every request, rules should be cloned.
Merge branch 'fix-csp-rule-forget' of github.com:purposeindustries/helmet into fix-csp-rule-forget
Merge branch 'fix-csp-rule-forget' of github.com:purposeindustries/helmet into fix-csp-rule-forget
do not slice the original directives