Update dependency i18next-xhr-backend to v3.1.1

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
i18next-xhr-backend	dependencies	minor	3.0.0 -> 3.1.1

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Release Notes

i18next/i18next-xhr-backend

### [`v3.1.1`](https://togithub.com/i18next/i18next-xhr-backend/blob/master/CHANGELOG.md#​311) [Compare Source](https://togithub.com/i18next/i18next-xhr-backend/compare/v3.1.0...v3.1.1) - typescript: fix use of class, add `use()` tests [322](https://togithub.com/i18next/i18next-xhr-backend/pull/322) ### [`v3.1.0`](https://togithub.com/i18next/i18next-xhr-backend/blob/master/CHANGELOG.md#​310) [Compare Source](https://togithub.com/i18next/i18next-xhr-backend/compare/v3.0.1...v3.1.0) - allow customHeaders to be a function [321](https://togithub.com/i18next/i18next-xhr-backend/pull/321) ### [`v3.0.1`](https://togithub.com/i18next/i18next-xhr-backend/blob/master/CHANGELOG.md#​301) [Compare Source](https://togithub.com/i18next/i18next-xhr-backend/compare/v3.0.0...v3.0.1) - typescript: Fix the types and use exposed types from i18next [319](https://togithub.com/i18next/i18next-xhr-backend/pull/319)

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