Update dependency xmldom

Switching from package `xmldom` to `@xmldom/xmldom`, which resolves the security issue present in latest xmldom version 0.6.0:
GHSA-5fg8-2547-mr8q

The reason is that the maintainers were forced to switch to a scoped package since 0.7.0:
 xmldom/xmldom#271

- I used node 12 to run `npm install`.
- I executed `npm run test` on my machine, but it failed because of some missing file:
```
[...]
> seriate@4.0.0 test:only /run/media/karfau/hdd-data/dev/seriate
> NODE_ENV=test mocha --exit -r spec/init -R spec 'spec/**/*.spec.js'

Browserslist: caniuse-lite is outdated. Please run:
npx browserslist@latest --update-db

Why you should do it regularly:
https://github.com/browserslist/browserslist#browsers-data-updating

Error: Cannot find module './local-config.json'
Require stack:
- /run/media/karfau/hdd-data/dev/seriate/spec/integration/one-connection.spec.js
[...]
```
- I executed `npm run test:ci` onmy machine without failure

I'm one of the xmldom maintainers. Don't hesitate to ask me questions.

package.json

@@ -51,13 +51,13 @@
     }
   ],
   "dependencies": {
+    "@xmldom/xmldom": "^0.8.0",
     "callsite": "^1.0.0",
     "debug": "^4.3.1",
     "lodash": "^4.17.21",
     "machina": "^4.0.2",
     "mssql": "~2.3.2",
-    "tedious": "~1.13.2",
-    "xmldom": "^0.6.0"
+    "tedious": "~1.13.2"
   },
   "devDependencies": {
     "chai": "^4.3.4",

src/asTable.js

@@ -1,6 +1,6 @@
 const _ = require( "lodash" );
 const sql = require( "mssql" );
-const xmldom = require( "xmldom" );
+const xmldom = require( "@xmldom/xmldom" );
 const domImplementation = new xmldom.DOMImplementation();
 const xmlSerializer = new xmldom.XMLSerializer();
 const buildTableVariableSql = require( "./build-table-variable-sql" );