Add generateDateTimePlusMinutes and generateDateTimePlusSeconds

What's Changed

• Add generateDateTimePlusMinutes by @Marketionist in #29
• Add generateDateTimePlusSeconds by @Marketionist in #30
• Add tests for currentDateTimePlus Minutes/Seconds by @Marketionist in #31
• Add examples for generateDateTimePlus Minutes/Seconds by @Marketionist in #32

Full Changelog: v1.3.0...v1.4.0