ibm-plex-otf: update to 5.2.1.

v5.2.1:

IBM Plex Sans JP:

Added:

- CSS stylesheets: css/ibm-plex-sans-jp.css and css/ibm-plex-sans-jp.min.css
- Sass entrypoint: scss/sans-jp/index.scss

The upcoming major release will make chosing specific font-weights and
languages easier for developers. Until then, enjoy IBM Plex Sans JP!

v5.1.3:

IBM Plex Sans KR:

Fixed:

- WWS naming scheme to make sure all weights are grouped together on certain
  versions of Windows referenced in #326

v5.1.0:

IBM Plex Sans KR Styles:

- CSS stylesheets: css/ibm-plex-sans-kr.css and css/ibm-plex-sans-kr.min.css
- Sass entrypoint: scss/sans-kr/index.scss

Rendering CJK fonts performantly on the web requires many more subsets
than western languages. These additional subsets result in many more
font-family declarations. Adding these declarations to the currently
generated stylesheet would cause it to double in size.

For this reason, we've split IBM Plex Sans KR off into it's own style
sheet. In the future, we'll be exporting similar stylesheets per-language
so developers can chose inidividual languages to suit their users.

v5.0.0:

New font file updates for:

- IBM Plex Sans
- IBM Plex Serif
- IBM Plex Sans Condensed
- IBM Plex Mono

This includes some changes to the vertical metrics of the font files as
well as a few changes to the available glyphs.

Breaking:

- Changed IBM Plex Sans Condensed to IBM Plex Sans Cond, this won't impact
  web applications, but could for other third party applications

New:

- IBM Plex Sans KR (Korean)


(fcambus)