Improve contributing.md

[hhkaos]

I'm bringing too many topics on this issue, and maybe some can be discussed in the future when PR start coming, but I wanted us to be aware that contributing guides can be tricky ^_^.

I would try to keep it short but at the same time define the most important rules like:

• Use the following format: [Item Name](link) - A short description ends with a period (Keep descriptions concise)
• Do we only add resources with free access or free tiers?
• Link additions should be added in alphabetical order of the relevant category.
• What's allowed and what's not, for example:

  • Do we allow a resource in multiple categories?

  • Do we allow beta/alpha projects?

  • I guess we allow multiple links to the same domain, right?:

    • developers.arcgis.com/documentation, developers.arcgis.com/arcgis-rest-js/....
    • but also: blog articles, training courses, ... <- or if there is a way to list and filter resources (like developer blog, Scripting & Development courses) we just point to it?

  • I guess new categories or improvements to the existing categorization are welcome.

  • Do we allow any resource that can be useful for a developer, no matter who made it?, let me raise a controversial one 😉 -> QGIS could be a source?, PostGIS?, Turf?, ... (I personally think... we should)

  • How many Category levels do we allow? 1, 2, ...?

  • Do we allow more than one link per line? for example:

    • ArcGIS Web Map Viewer: Create, explore, and share web maps for 2D applications (classic version)
    • Esri Developer Summit Plenary Sessions: 2021, 2020, 2019, 2018, 2017 and 2016
• What do we do with localized resources?, imagine there are things that make sense to highlight but only in Spain, or only in the US? (like awesome datasets?) do we create a folder local awesomes?
• I guess we don't want to add too many resources per each specific ArcGIS API or Service, right?
• Make an individual pull request for each suggestion.
• Search previous suggestions before making a new one, as yours may be a duplicate.
  The pull request and commit should have a useful title.

Other contributing.md: awesome-eslint, awesome-geojson, awesome-awesome

[hhkaos]

sorry @jf990 I forgot to mention you here 😉