Fix and improve highlighting with highlight.js

[mmattel]

References: owncloud/docs-server#94 ([QA] Manual copy / paste misses redirects)
References: owncloud/docs#4707 (Add info for the correct use of the source langauge)

Description:

• When using a language for examples (Antora source block), it is crucial to use the correct one. There is a big difference between using console (shell.js) and bash (bash.js). While bash highlights any recognized bash keyword word from the beginning and let this also be selectable via CSS in the browser, console requires mandatory a bash promt at the beginning to highlight bash keywords correctly - but additionally disables the bash prompt as selectable component in the browser
• The color of the language selected is now the same color as a bash keyword, which makes the language much better distinctable from the below example block
• The language selected + the copy symbol are moved up a bit to make it not that close to the example block
• Additional keywords are added dynamically to the bash language reflecting available commands when a application is installed providing these commands like phpen/dismod or wget ect, see: Adding Keywords to a Language at Startup. Some keywords are added in advance like the a2xxx commands and will automatically be highlighted when the next release of highlight.js gets published, see: enh(bash) $pattern: allow numbers after the first character highlightjs/highlight.js#3494
• The occ keyword has been added to the above list

NOTE:

• This PR is the base that things CAN get highlightable correctly. It is essential to use the correct language in the documentation - additional changes may be necessary there. For details using the correct language see the referenced docs PR.
• The descriptions are added intentionally to understand the behaviour and the reason. This info are hard to find and therefore worth to document it here.

Examples:
(The examples below already reflect a correct language used)

@jnweiger fyi

[xoxys]

@mmattel I would definitely not recommend it.

[xoxys]

That is simply not true. Someone could sneak in evil code in a docs PR, and it can get merged by someone who is not aware of this potential issue. Why not simply escape the HTML within code blocks as recommended? There is no real reason to disable security mechanisms.

[mmattel]

ok, thanks for the insight. I will open a new issue.