feat: preserve sha1 integrity and auto detect lockfile (#10)

* bug: added `--preserve-integrity` flag to prevent removal of integrity hash when `sha1` is used due to private repositories such as Azure Artifacts not supporting anything other than `sha1`.

feat: removed need for `--lockfile` flag if a `yarn.lock` or `package-lock.json` exists. Defaults to `yarn.lock` if not found. You can still specify a lockfile if you wish.

chore: updated eslint-plugin-import to ^2.31.0 for eslint 9 support

* Tweaked the lockFileName detector code as per feedback

* Changed isYarn check to be more explicit with filename

chore: backport fork changes to upstream (#7)

* feat: v5

* docs: license

* docs: add section r.e. alternatives

* fix: correctly handle ignores even if limited to administrators

* fix: ensure the expiry date is 30 days in future and not today

* chore: eslint v9 upgrade

* fix: need to force install to workaround incorrect peer deps on npm

[#3] Remove hardcoded snyk path (#4)

[NO-ISSUE] Fix readme to use `@asos` scope (#2)

[NO-ISSUE] Scoped package (#1)