chore(deps): update dependency isbot to v5.1.8 (#264)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [isbot](https://isbot.js.org)
([source](https://togithub.com/omrilotan/isbot)) | [`5.1.7` ->
`5.1.8`](https://renovatebot.com/diffs/npm/isbot/5.1.7/5.1.8) |
[![age](https://developer.mend.io/api/mc/badges/age/npm/isbot/5.1.8?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/npm/isbot/5.1.8?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/npm/isbot/5.1.7/5.1.8?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/npm/isbot/5.1.7/5.1.8?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

---

### Release Notes

<details>
<summary>omrilotan/isbot (isbot)</summary>

###
[`v5.1.8`](https://togithub.com/omrilotan/isbot/blob/HEAD/CHANGELOG.md#518)

[Compare
Source](https://togithub.com/omrilotan/isbot/compare/v5.1.7...v5.1.8)

- \[Pattern] Recognise timestamp in user agent string - is used to
generate unique strings for each request

</details>

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