classes: Rename Riot to Element

[jtojnar]

https://element.io/blog/welcome-to-element/

[codecov]

Codecov Report

Merging #278 (c352418) into master (778f379) will not change coverage.
The diff coverage is n/a.

❗ Current head c352418 differs from pull request most recent head aa81bf1. Consider uploading reports for the commit aa81bf1 to get more accurate results

@@           Coverage Diff           @@
##           master     #278   +/-   ##
=======================================
  Coverage   20.78%   20.78%           
=======================================
  Files          26       26           
  Lines        1318     1318           
  Branches      174      174           
=======================================
  Hits          274      274           
  Misses       1002     1002           
  Partials       42       42           

Impacted Files	Coverage Δ
src/util/classes.ts	84.61% <ø> (ø)

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