Feat: in GitHub issie include document modified date (mdn#2569)

* Feat: in GitHub issie include document modified date

* Fix: handle case when doc.modified is null

Add Background Fetch Spec (mdn#2636)

Adding relative indexing method (at()) to specdata (mdn#2637)

* Updating contact picker

It's a singular 'Contact Picker API' - it was added as 'Contact*s* Picker API'

* adding relative indexing method to specdata

Quick_Links or Quick_links, both are OK (mdn#2633)

Fixes mdn#2632

chore: unnecessary-pass (mdn#2624)

fix incomplete change from pull request 2622 (mdn#2631)

build(deps-dev): bump downshift from 6.0.16 to 6.1.0 (mdn#2628)

fix: pylint redefined-outer-name (mdn#2622)

chore: Add missing webpack peerDep (mdn#2479)

Matched version used by react-script pack

chore: Add missing ESLint peerDep (mdn#2480)

Still meets react-script dep of `eslint "^7.11.0"`, but fixes warnings
for other ESLint plugins