Add Nanum Barun Gothic

**Font Project Git Repo URL:**

https://github.com/hiun/NanumBarunGothic - although this is a 3rd party repo, I doubt the original has a repo.

**Super short description of the Font Family:**

The famous Nanum fonts were a set of OFL fonts released by Naver (a Korean tech company) in the early days of web fonts. Turns out I didn't add `Barun Gothic` to Early Access for reasons unknown (possibly it came out later that the others).

**Requirements:**

I understand that Google Fonts will publish only fonts that matches its requirements, and I can confirm the project meets them (by ticking the cases, or putting x between the square brackets in text mode):

- [x] The entire font project is licensed under the [OFL](https://scripts.sil.org/cms/scripts/page.php?site_id=nrsi&id=OFL)
- [ ] **There is a "Reserved Font Name" mention in the OFL license** but Google has permission to use the RFNs.
- [x] Family name is unique according to namecheck.fontdata.com
- [x] If the font targets latin based written languages, it supports at least [GF Latin Core glyphset](https://github.com/googlefonts/gftools/blob/main/Lib/gftools/encodings/GF%20Glyph%20Sets/GF-latin-core_unique-glyphs.nam)
- [x] I read and agree with the full [contributing requirements](https://github.com/google/fonts/blob/main/CONTRIBUTING.md)
- [ ] **The repository does not respect the [upstream repo structure](https://github.com/googlefonts/gf-docs/tree/main/Spec#upstream-repo-structure)** and probably we should make our own.
- [x] I will maintain the repository