Add the early version of query-ops implmenation

crates/query-ops/README.md

@@ -18,15 +18,17 @@ The operators are: atom scan, semijoin, and natural join.
 
 <div align="center">
   <picture>
-    <img alt="Types" src="docs/diagrams/types.svg" height="70%" width="70%">
+    <img alt="Types" src="docs/diagrams/types.svg" height="50%" width="50%">
   </picture>
 </div>
 
 ### Example
 
 The rule below returns the authors of every bestseller along with the book's price.
-It uses all three operators: `scan_atom` for the three input tables, `semijoin` to keep only authors of bestsellers, and `natural_join` to attach each
-book's price.
+It uses all three operators:
+- `scan_atom` for the three input tables,
+- `semijoin` to keep only authors of bestsellers,
+- and `natural_join` to attach each book's price.
 
 ```text
 Q(name, book, dollars) :- author(name, book), bestseller(book), price(book, dollars).
@@ -102,9 +104,11 @@ fn main() {
 }
 ```
 
+How it works:
+
 <div align="center">
   <picture>
-    <img alt="Types" src="docs/diagrams/architecture.svg" height="70%" width="70%">
+    <img alt="Types" src="docs/diagrams/workflow.svg" height="90%" width="90%%">
   </picture>
 </div>