Roadmap info!

Browsing and noticed that 2014 and 2024 have differences, which makes sense given 2024 is new. I believe a ROADMAP could be handy for folks to help out & know what is already being worked on. I see:

```javascript
// 2014 resources
[
"ability_scores",
"alignments",
"backgrounds",
"classes",
"conditions",
"damage_types",
"equipment",
"equipment_categories",
"feats",
"features",
"languages",
"levels",
"magic_items",
"magic_schools",
"monsters",
"proficiencies",
"races",
"rule_sections",
"rules",
"skills",
"spells",
"subclasses",
"subraces",
"traits",
"weapon_properties"
]
// 2024 resources
[
"ability_scores",
"alignments",
"backgrounds",
"conditions",
"damage_types",
"equipment",
"equipment_categories",
"feats",
"languages",
"magic_schools",
"proficiencies",
"skills",
"weapon_mastery_properties",
"weapon_properties"
]
```
I bet Monsters will be quite the undertaking, given the 2024 changes.

Look at the repository's README and existing documentation to understand the structure of the 2014 and 2024 data. Identify where roadmap information could be added, such as a ROADMAP.md file. Compare the two resource lists provided in the issue to determine missing endpoints and plan for their implementation.

Written by the indexing model from the issue text.