Install Mediawiki Extensions: InputBox, Gadgets and VE

## Problem Description

There are a number of useful MediaWiki extensions that are not enabled in this wiki. The suggested list includes:

- [Extension:InputBox](https://www.mediawiki.org/wiki/Extension:InputBox), Allows to setup forms in contexts that user input is needed, such as facilities for searching through existing case studies before submitting new one as an example.
- [Extension:Gadgets](https://www.mediawiki.org/wiki/Extension:Gadgets), Allows incorporation of even more tools and the facility to enable/disable them in the user preferences.
- [Extension:VisualEditor](https://www.mediawiki.org/wiki/Extension:VisualEditor), Allows editing markups that are rather time consuming via wikitext in an intuitive way (such as adding or removing columns to.from wikitables)

## Solution Description

Some extensions are pre-installed in MediaWiki-1.30.0 by default and just need enabling in LocalSettings.php via a few configuration lines (such as Gadgets and InputBox). Some extensions need to be downloaded separately from MediaWiki extension distribution portal (such as Visual Editor) and require additional dependencies to be installed.

## Alternatives

Since possibly wiki is in some sort of maintenance period, it might be better to enable or install new extensions after upgrading to the next release of Mediawiki such as 1.31.6 (LTS) or 1.34.0 (Stable).

## Additional context

None