fix a handful of strict null errors; make test config also be strict

These errors only arose because I didn't run `npm build`, only `npm
test`. Then, when I tried building the null checks failed. Keeping the
two config fiels in sync will help prevent this issue in the future

ts/docx/table/index.ts

@@ -23,7 +23,7 @@ export class Table extends XmlComponent {
 
         this.rows = [];
         for (let i = 0; i < rows; i++) {
-            const cells = [];
+            const cells: TableCell[] = [];
             for (let j = 0; j < cols; j++) {
                 cells.push(new TableCell());
             }