input: Add experimental rich-text support (#315)

This adds an experimental csl-rich-text.yaml schema that defines a
structure for rich-text formatting in JSON.

Also adds a definition for rich-text variables, and title-string
definitions that uses that variable, and then redefines all title and
other fields to use these definitions. So it will be easy to merge the
rich text support in the future.

Addresses in part #278

schemas/input/csl-data.json

@@ -221,10 +221,10 @@
         "$ref": "#/definitions/date-variable"
       },
       "abstract": {
-        "type": "string"
+        "$ref": "#/definitions/rich-text-string"
       },
       "annote": {
-        "type": "string"
+        "$ref": "#/definitions/rich-text-string"
       },
       "archive": {
         "type": "string"
@@ -257,13 +257,13 @@
         "type": ["string", "number"]
       },
       "collection-title": {
-        "type": "string"
+        "$ref": "#/definitions/title-string"
       },
       "container-title": {
-        "type": "string"
+        "$ref": "#/definitions/title-string"
       },
       "container-title-short": {
-        "type": "string"
+        "$ref": "#/definitions/title-string"
       },
       "dimensions": {
         "type": "string"
@@ -344,7 +344,7 @@
         "type": "string"
       },
       "original-title": {
-        "type": "string"
+        "$ref": "#/definitions/title-string"
       },
       "page": {
         "type": ["string", "number"]
@@ -356,7 +356,7 @@
         "type": ["string", "number"]
       },
       "part-title": {
-        "type": "string"
+        "$ref": "#/definitions/title-string"
       },
       "PMCID": {
         "type": "string"
@@ -377,7 +377,7 @@
         "type": "string"
       },
       "reviewed-title": {
-        "type": "string"
+        "$ref": "#/definitions/title-string"
       },
       "scale": {
         "type": "string"
@@ -395,16 +395,16 @@
         "type": ["string", "number"]
       },
       "title": {
-        "type": "string"
+        "$ref": "#/definitions/title-string"
       },
       "title-short": {
-        "type": "string"
+        "$ref": "#/definitions/title-string"
       },
       "translated-title": {
-        "type": "string"
+        "$ref": "#/definitions/title-string"
       },
       "translated-title-short": {
-        "type": "string"
+        "$ref": "#/definitions/title-string"
       },
       "URL": {
         "type": "string"
@@ -437,6 +437,16 @@
     "additionalProperties": false
   },
   "definitions": {
+    "rich-text-string": {
+      "title": "Rich Text String",
+      "description": "A string that may include sub-string formatting for bold, italic, subscript, superscript, math, etc. The accompanying `csl-rich-text.yaml` schema defines experimental support for this in CSL JSON input.",
+      "type": "string"
+    },
+    "title-string": {
+      "title": "Title String",
+      "description": "Titles are a primary example of rich text strings in CSL.",
+      "$ref": "#definitions/rich-text-string"
+    },
     "edtf-string": {
       "title": "EDTF date string",
       "description": "CSL input supports EDTF, levels 0 and 1.",

schemas/input/csl-rich-text.yaml

@@ -0,0 +1,54 @@
+---
+description: JSON schema for CSL input rich text representation
+"$schema": http://json-schema.org/draft-07/schema#
+"$id": https://resource.citationstyles.org/schema/latest/input/json/csl-rich-text.json
+definitions:
+  rich-text-content:
+    title: Rich Text Content
+    description: Rich text content can be represented as an array of strings and formatted object strings.
+    examples:
+      - title:
+          - A title with a
+          - quote: quoted string.
+      - title:
+          - A title with tex math
+          - math-tex: x=y^2
+      - title:
+          - A title with mathml
+          - math-ml: x=y^2
+    oneOf:
+      - "$ref": "#/definitions/rich-text"
+      - type: string
+  rich-text:
+    type: array
+    items:
+      anyOf:
+        - title: Unformatted Sub-String
+          type: string
+        - bold:
+            title: Bold Text
+            "#ref": "#/definitions/rich-text-content"
+        - code:
+            title: Code/Verbatim Text
+            "#ref": "#/definitions/rich-text-content"
+        - italic:
+            title: Italicized Text
+            "#ref": "#/definitions/rich-text-content"
+        - math-ml:
+            title: MathML
+            "#ref": "#/definitions/rich-text-content"
+        - math-tex:
+            title: Math-TeX
+            "#ref": "#/definitions/rich-text-content"
+        - preserve:
+            title: Preserve Case Text
+            "#ref": "#/definitions/rich-text-content"
+        - quote:
+            title: Quote
+            "#ref": "#/definitions/rich-text-content"
+        - sc:
+            title: Small-Cap Text
+            "#ref": "#/definitions/rich-text-content"
+        - strike:
+            title: Strike-Through Text
+            "#ref": "#/definitions/rich-text-content"