Update html-to-text to fix uncontrolled memory consumption

[sseide]

Current version of prod dependency html-to-text has a problem rendering specially crafted html templates leading to a memory exhaustion on the server running this code. A fix (with high memory limits to stop this kind of attack) and options to better control this behaviour for untrusted content was applied to html-to-text@6.0.0

This PR updates the html-to-text library to the latest 7.x release.
When using options passed to html-to-text they must be re-evaluated with the html-to-text documentation as release 6.x changed some of them. Update instructions can be found on the github page https://github.com/html-to-text/node-html-to-text

Note: This update needs at least NodeJS 10.23, older node releases are not supported by html-to-text. But Node 8.x and older is End-of-life for some time by now and everyone should have updated, therefore not a problem.

Together with this prod dependency i updated dev dependencies mocha and grunt fixing multiple security warnings within their own dependencies and fixed the deprecated usage of new Buffer() within the test cases.

All tests are green and within our own apps the updated version works too without any problems, only options needed to be adapted.

More information about the problem can be found here: https://app.snyk.io/vuln/SNYK-JS-HTMLTOTEXT-571464 and html-to-text/node-html-to-text#172

Please release a new version to NPM afterwards. As these fix contains breaking changes (minimum NodeJS and option handling) a major version update may be recommended.

Thanks,
Stefan Seide

[andris9]

Published as v3.2.0

[sseide]

Many thanks for the fast response.