Avoid redundant re-rendering

[takakobem]

Context value should be memoized to avoid re-rendering in consumer components.
Actually, when I18nProvider is re-rendered event if props are not changed, value object is recreated and all consumer components are re-rendered.

Checklist

• only relevant code is changed (make a diff before you submit the PR)
• run tests npm run test
• tests are included
• documentation is changed or added

[coveralls]

Coverage increased (+0.02%) to 95.692% when pulling 7c83a8e on takakobem:avoid-unnecessary-rerendering into afeaebb on i18next:master.

[jamuhl]

Good catch...👍

[jamuhl]

published in react-i18next@11.7.3