Updated README with Riot->Element and end user documentation

Port to ESLint (continuation)

Merge branch 'j94/remove-unused-provisioner' of https://github.com/jaller94/matrix-appservice-discord into develop

Merge branch 'j94/invalid-log-levels' of https://github.com/jaller94/matrix-appservice-discord into develop

Merge branch 'j94/metrics-config' of https://github.com/jaller94/matrix-appservice-discord into develop

Merge branch 'no-discordapp' of https://github.com/auscompgeek/matrix-appservice-discord into develop

Merge branch 'j94/substr-to-substring' of https://github.com/jaller94/matrix-appservice-discord into develop

Merge branch 'j94/riot-to-element' of https://github.com/jaller94/matrix-appservice-discord into develop

Merge branch 'j94/chai-expect' of https://github.com/jaller94/matrix-appservice-discord into develop

"-m" flag in the "npm run adminme" command seems to be deprecated. Changed to the appropriate "-r" flag.

Add /health HTTP endpoint