Add MegaLinter

[jtxa]

Adds a GitHub workflow for MegaLinter with initial configuration and some fixed.

Successful linters:

• Bash: bash-exec, shellcheck, shfmt
• Editorconfig
• JSON: eslint-plugin-jsonc, jsonlint, prettier, v8r
• Markdown: markdownlint, markdown-link-check, markdown-table-formatter
• Repository: gitleaks, git_diff, secretlint
• Spelling: cspell, misspell
• YAML: prettier, v8r, yamllint

Switched to be non-blocking:

• CPP: cpplint - out of scope of this PR; changes would need more detailed reviews
• HTML: djlint, htmllint - out of scope of this PR; files in git have troff commands and rest is generated

[jtxa]

I kept the shell script reformatting in separate commits from the changes (for now). For an easier review to decide if the format is now ok (I used some configuration values to match existing formatting as close as possible).

[jtxa]

@sierrafoxtrot Please have a look at the questions above. If you tell me your preference, I can make this PR ready for merge.

[sierrafoxtrot]

Adds a GitHub workflow for MegaLinter with initial configuration and some fixed.

Successful linters:

* JSON: eslint-plugin-jsonc, jsonlint, prettier, v8r

Curious about this one. We don't have any JSON or JS from memory. Does this cover something I'm forgetting?

[jtxa]

The new cSpell configuration is currently a JSON file. But I take a look to convert it to YAML, that way comments can also be added and it might look a bit easier.

[sierrafoxtrot]

The new cSpell configuration is currently a JSON file. But I take a look to convert it to YAML, that way comments can also be added and it might look a bit easier.

I understand. This work is a huge leap forward Josef so happy to keep it as-is if that is the simplest way forward.

[jtxa]

A little polishing done here and there since the first push. The major ones are:

• cSpell configuration as YAML: better readability and comments added why some settings were made.
• All YAML files with indent of 2, everything else looks weird because of the arrays using -.
• I did check if all the output of the doc scripts is the same as before, and now they are (see #21).

From my side this PR is ready now.

[jtxa]

Rebase to solve conflicts. Also deleted shell/awk/ignore files, obsolete after #22

[jtxa]

• Rebased
• Doc-CMake changes splitted to mulitple commits with revised content and messages
• I reverted some of my ci.yml changes. There will be a follow-up PR with Windows and MacOS build added.
• The rest is the same as before. I repeated my check that the generated documentation is still the same.