feat(nodejs): expose computed columns and refreshColumn

addComputedColumns declares columns defined by a SQL expression, and
refreshColumn fills a computed column's unfilled rows:

    await table.addComputedColumns([{ name: "doubled", valueSql: "x * 2" }]);
    await table.refreshColumn("doubled");

docs/src/js/classes/Table.md

@@ -71,7 +71,12 @@ Add new columns with defined values.
 
 #### Parameters
 
-* **newColumnTransforms**: `Field`<`any`> \| `Field`<`any`>[] \| `Schema`<`any`> \| [`AddColumnsSql`](../interfaces/AddColumnsSql.md)[]
+* **newColumnTransforms**:
+    \| `Field`<`any`>
+    \| `Field`<`any`>[]
+    \| `Schema`<`any`>
+    \| [`AddColumnsSql`](../interfaces/AddColumnsSql.md)[]
+    \| `object`
     Either:
     - An array of objects with column names and SQL expressions to calculate values
     - A single Arrow Field defining one column with its data type (column will be initialized with null values)
@@ -718,6 +723,28 @@ for await (const batch of table.query()) {
 
 ***
 
+### refreshColumn()
+
+```ts
+abstract refreshColumn(column): Promise<RefreshColumnResult>
+```
+
+Compute and store values for a computed column's unfilled rows.
+
+#### Parameters
+
+* **column**: `string`
+    The name of the computed column to fill.
+
+#### Returns
+
+`Promise`&lt;[`RefreshColumnResult`](../interfaces/RefreshColumnResult.md)&gt;
+
+A promise that resolves to the
+number of rows filled and the new version number of the table.
+
+***
+
 ### restore()
 
 ```ts