Revert "Revert "TypeScript Improvement: Use [key: string]: unknown, not [key: string]: any (#3565)""

This reverts commit 81d2f9bb8f.

docs/concepts/01-interfaces.md

@@ -5,7 +5,7 @@ Slate works with pure JSON objects. All it requires is that those JSON objects c
 ```ts
 interface Text {
   text: string
-  [key: string]: any
+  [key: string]: unknown
 }
 ```
 
@@ -22,7 +22,7 @@ To take another example, the `Element` node interface in Slate is:
 ```ts
 interface Element {
   children: Node[]
-  [key: string]: any
+  [key: string]: unknown
 }
 ```
 

docs/concepts/02-nodes.md

@@ -55,7 +55,7 @@ Elements make up the middle layers of a richtext document. They are the nodes th
 ```ts
 interface Element {
   children: Node[]
-  [key: string]: any
+  [key: string]: unknown
 }
 ```
 
@@ -126,7 +126,7 @@ Text nodes are the lowest-level nodes in the tree, containing the text content o
 ```ts
 interface Text {
   text: string
-  [key: string]: any
+  [key: string]: unknown
 }
 ```
 

docs/concepts/03-locations.md

@@ -37,7 +37,7 @@ Points are slightly more specific than paths, and contain an `offset` into a spe
 interface Point {
   path: Path
   offset: number
-  [key: string]: any
+  [key: string]: unknown
 }
 ```
 
@@ -71,7 +71,7 @@ Ranges are a way to refer not just to a single point in the document, but to a w
 interface Range {
   anchor: Point
   focus: Point
-  [key: string]: any
+  [key: string]: unknown
 }
 ```
 

docs/concepts/06-editor.md

@@ -8,7 +8,7 @@ interface Editor {
   selection: Range | null
   operations: Operation[]
   marks: Record<string, any> | null
-  [key: string]: any
+  [key: string]: unknown
 
   // Schema-specific node behaviors.
   isInline: (element: Element) => boolean