Update the documentation for new developers

[bernhardkaindl]

This PR updates the documentation for new developers.

It is focused on writing unit tests for now, aimed at:

• assuring that the Python3 migration is complete and does not have defects
• testing all (more or less) recently implemented capabilities to work on current XS8 and fixing any issues that are (and have already) been found (see #58) in the process.

In general:

• This is only the initial update of the documentation for new developers
  • There will very likely be more updates as onboarding of new developers
• It is written using the LTEX Extension for VS Code: Grammar/Spell Checker Using LanguageTool with Support for LATEX, Markdown, and Others

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (eb9a639) 85.55% compared to head (1628773) 85.55%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #60 +/- ## ======================================= Coverage 85.55% 85.55% ======================================= Files 16 16 Lines 2021 2021 ======================================= Hits 1729 1729 Misses 292 292 ``` | [Flag](https://app.codecov.io/gh/xenserver/status-report/pull/60/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=xenserver) | Coverage Δ | | |---|---|---| | [python2.7](https://app.codecov.io/gh/xenserver/status-report/pull/60/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=xenserver) | `84.06% <ø> (ø)` | | | [python3.10.13](https://app.codecov.io/gh/xenserver/status-report/pull/60/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=xenserver) | `84.72% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=xenserver#carryforward-flags-in-the-pull-request-comment) to find out more.

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