Add DEFAULT_EXP_DUMMY_CERT and set to 90 days
Add DEFAULT_EXP_DUMMY_CERT and set to 90 days

Helps with Chrome's "certificates can not be valid longer than 27,5 month"
Fixes #3273

mhils/mitmproxy,vhaupert/mitmproxy,mhils/mitmproxy,mhils/mitmproxy,vhaupert/mitmproxy,mitmproxy/mitmproxy,Kriechi/mitmproxy,vhaupert/mitmproxy,Kriechi/mitmproxy,mitmproxy/mitmproxy,vhaupert/mitmproxy,mitmproxy/mitmproxy,mitmproxy/mitmproxy,mitmproxy/mitmproxy,mhils/mitmproxy,mhils/mitmproxy,Kriechi/mitmproxy,Kriechi/mitmproxy