Pre-onboarding template for designers

WIP

I had a discussion with @RosaWagner about how improve our onboarding process, especially how to help designers prepare their files.
In order to help designers to control their project as much as possible and not to be surprised by all the changes we make according to the GF specs, we could provide them this simplified guide, which will be a kind of checklist to follow (we still need to define what form this will take).
This checklist can be linked to each corresponding chapter in the guide.

This is just the structure, I added few points but there will be many things to complete as we go along.

#### Repo
- [ ] [Repo Structure](https://googlefonts.github.io/gf-guide/upstream)

#### Font infos
- [ ] [Font name](https://googlefonts.github.io/gf-guide/requirements.html#font-name)
- [ ] [Copyright and license strings](https://googlefonts.github.io/gf-guide/license-file.html)
- [ ] [Version number](https://googlefonts.github.io/gf-guide/requirements.html#font-versioning)

#### Outlines
- [ ] [Segments](https://googlefonts.github.io/gf-guide/outlines.html#segments)
- [ ] [Nodes](https://googlefonts.github.io/gf-guide/outlines.html#on-curve-points-nodes)
- [ ] [Components](https://googlefonts.github.io/gf-guide/outlines.html#components)
- [ ] Special interpolation (alternate layers, rvrn feature etc.)

## For Latin fonts

#### Glyphset
- [ ] [Glyphset](https://googlefonts.github.io/gf-guide/requirements.html#glyph-sets)
- [ ] Glyphs names: prod names, nice names, unicode ?
- [ ] OpenType features

#### Accents
- [ ] Accented composite glyphs (auto-alignement / combining accents / anchors on every base glyphs)
- [ ] [Anchors](https://googlefonts.github.io/gf-guide/diacritics.html#anchors) alignement
- [ ] [Legacy marks](https://googlefonts.github.io/gf-guide/diacritics.html#legacy--spacing-marks) are created by using the combining marks as components and have a positive advance width value ≠0.
- [ ] [Localisation and Special glyphs](https://googlefonts.github.io/gf-guide/diacritics.html#special-glyphs)

#### Spacing and Kerning
- [ ] Groups
- [ ] List of main pairs
- [ ] Kerning tools

#### [Vertical Metrics](https://googlefonts.github.io/gf-guide/metrics.html)
- [ ] Use_Typo_Metrics is enabled.
- [ ] typoAscender and hheaAscender set higher than À
- [ ] typoLineGap and hheaLineGap set to 0
- [ ] typoDescender and hheaDescender set lower than the deepest descender of the primary script.
- [ ] winAscent and winDecent set to yMax and yMin (absolute highest and lowest point in the font

#### Style Naming
- [ ] [The RIBBI convention](https://googlefonts.github.io/gf-guide/statics.html)

### Variable Font
- [ ] Axes
- [ ] STAT
- [ ] FVAR
- [ ] AVAR
- [ ] Conventions for wght, wdth, opsz, ital