Add examples

What's Changed

• Update go version to 1.20.6 by @devlights in #657
• Add slice_append_special_behavior example by @devlights in #658
• Update Go version by @devlights in #659
• Add Go 1.21 min,max example by @devlights in #660
• Add find number of digits example by @devlights in #662
• Add speeds for setting strings to byteslice by @devlights in #663

Full Changelog: v0.5.1...v0.5.2