update CHANGELOG.md for v0.1.8

add more test cases

support parsing time zone offset with `%:::z`

optimize compound directives by resolving in switch statement

refactor %G and %g parsing to reuse %Y and %y

fix %s for 32-bit platforms, optimize formatting integers

add benchmarks for formatting and parsing

support parsing negative numbers (%Y, %G, %s)

add test with Go 1.26

fix %g parsing to use the same threshold as %y

fix formatting of negative numbers (%Y, %C, %y, %g, %s)

update CHANGELOG.md for v0.1.7

update copyright year in LICENSE

bump up GitHub Actions versions

add fuzzing tests for format and parse functions