Restructuring Rules.json

### Summary

Combines `Rules.json` and `Rule-Sections.json` into a single file with self-referential links according to the following format:

```javascript
[
{
"name": "System Reference Document 5.1",
"index": "srd",
"url": "/api/rules/srd"
"children": [
{
"name": "Combat",
"index": "combat",
"url": "/api/combat"
},
// ...
},
{
"name": "Combat",
"index": "combat",
"url": "/api/rules/combat"
"desc": "...",
"parent": {
"name": "System Reference Document 5.1",
"index": "srd",
"url": "/api/srd"
},
"children": [
{
"name": "The Order of Combat",
"index": "the-order-of-combat",
"url": "/api/the-order-of-combat"
},
// ...
},
// ...
]
```

---

*Original text follows.*

Currently the rules are spread across two files, as follows:

```javascript
// 5e-SRD-Rules.json
[
{
"name": "Combat",
"index": "combat",
"desc": "# Combat\n",
"subsections": [
{
"name": "The Order of Combat",
"index": "the-order-of-combat",
"url": "/api/rule-sections/the-order-of-combat"
},
// ...
],
"url": "/api/rules/combat"
}
]

// 5e-SRD-Rule-Sections.json
[
{
"name": "The Order of Combat",
"index": "the-order-of-combat",
"desc": "## The Order of Combat\n\nA typical combat encounter is a clash between two sides, a flurry of weapon swings, feints, parries, footwork, and spellcasting. The game organizes the chaos of combat into a cycle of rounds and turns. A **round** represents about 6 seconds in the game world. During a round, each participant in a battle takes a **turn**. The order of turns is determined at the beginning of a combat encounter, when everyone rolls initiative. Once everyone has taken a turn, the fight continues to the next round if neither side has defeated the other.\n\n##### Combat Step by Step\n\n...",
"url": "/api/rule-sections/the-order-of-combat"
},
// ...
]
```

However, the current situation doesn't do a particularly good job of representing the data in either a human- or machine-readable format. For my own use case, I'd like to have much smaller text snippets for reference purposes, so that a user could search for "Bonus Actions" and see only the snippet . Most of the data from the SRD is digested into bite-sized pieces, so it's rather out of place to have these giant blobs of text in `5e-SRD-Rule-Sections.json`.

I suggest consolidating the rules down into a single file, with each heading getting its own entry.

```javascript
// 5e-SRD-Rules.json
[
{
"name": "Combat",
"index": "combat",
// no "desc" key at all as this heading continues directly into "The Order of Combat"
"subsections": [
{
"name": "The Order of Combat",
"index": "the-order-of-combat",
"url": "/api/rules/the-order-of-combat"
},
// ...
],
"url": "/api/rules/combat"
},
{
"name": "The Order of Combat",
"index": "the-order-of-combat",
// No title, includes all content to the next subheading
"desc": "A typical combat encounter is a clash between two sides, a flurry of weapon swings, feints, parries, footwork, and spellcasting. The game organizes the chaos of combat into a cycle of rounds and turns. A **round** represents about 6 seconds in the game world. During a round, each participant in a battle takes a **turn**. The order of turns is determined at the beginning of a combat encounter, when everyone rolls initiative. Once everyone has taken a turn, the fight continues to the next round if neither side has defeated the other.",
"subsections": [
{
"name": "Combat Step by Step",
"index": "combat-step-by-step",
"url": "/api/rules/combat-step-by-step"
},
// ...
],
"url": "/api/rule/the-order-of-combat"
},
{
"name": "Combat Step by Step",
"index": "combat-step-by-step",
"desc": "..."
"url": "/api/rules/combat-step-by-step"
// ...
]
```

Alternatively, a `parent_url` field could be added to the child rather than the `subsections` field on the parent. Either way, it would have to be associated with tests ensuring that there are no circular dependencies, there is only one root node, and there are no orphaned nodes. A bidirectional association is also possible for easier reading, but that would require extra test coverage to maintain consistency.