📝 Add docs annotations for source examples

docs_src/tutorial/select/annotations/en/tutorial002.md

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+1. Import from `sqlmodel` everything we will use, including the new `select()` function.
+
+2. Create the `Hero` class model, representing the `hero` table.
+
+3. Create the **engine**, we should use a single one shared by all the application code, and that's what we are doing here.
+
+4. Create all the tables for the models registered in `SQLModel.metadata`.
+
+    This also creates the database if it doesn't exist already.
+
+5. Create each one of the `Hero` objects.
+
+    You might not have this in your version if you had already created the data in the database.
+
+6. Create a new **session** and use it to `add` the heroes to the database, and then `commit` the changes.
+
+7. Create a new **session** to query data.
+
+    !!! tip
+        Notice that this is a new **session** independent from the one in the other function above.
+
+        But it still uses the same **engine**. We still have one engine for the whole application.
+
+8. Use the `select()` function to create a statement selecting all the `Hero` objects.
+
+    This selects all the rows in the `hero` table.
+
+9. Use `session.exec(statement)` to make the **session** use the **engine** to execute the internal SQL statement.
+
+    This will go to the database, execute that SQL, and get the results back.
+
+    It returns a special iterable object that we put in the variable `results`.
+
+    This generates the output:
+
+    ```
+    INFO Engine BEGIN (implicit)
+    INFO Engine SELECT hero.id, hero.name, hero.secret_name, hero.age 
+    FROM hero
+    INFO Engine [no key 0.00032s] ()
+    ```
+
+10. Iterate for each `Hero` object in the `results`.
+
+11. Print each `hero`.
+
+    The 3 iterations in the `for` loop will generate this output:
+
+    ```
+    id=1 name='Deadpond' age=None secret_name='Dive Wilson'
+    id=2 name='Spider-Boy' age=None secret_name='Pedro Parqueador'
+    id=3 name='Rusty-Man' age=48 secret_name='Tommy Sharp'
+    ```
+
+12. At this point, after the `with` block, the **session** is closed.
+
+    This generates the output:
+
+    ```
+    INFO Engine ROLLBACK
+    ```
+
+13. Add this function `select_heroes()` to the `main()` function so that it is called when we run this program from the command line.