- Do not check whether pages or sections are valid
- Check the entire form and if necessary the controls

- Check if the selection refers to the content of the text component

- Remove the manipulation of the end offset
- Add the end container of the selection to the list of the selected
nodes if end offset is 0

This disables the possibility of nested markers

When the user exits selecting between paragraphs, the offset of the
end container is set to 0. In Firefox this always (in Chrome sometimes)
leads to a misinterpretation of the selection. Therefore, the offset
is manipulated.

When the user finishes selecting between paragraphs and the selection
happens from back to front, Firefox does not consider the start
container as a selected child node. Therefore, it is added to the
list of selected nodes at the beginning.

The marking service takes over the conversion to rgb notation, because
in html markup this notation is used for the background color

When a page has longer scrollable dynamic content that consists of many
individual elements (Likert), the content was sometimes not displayed
after interacting with those elements. This happened in the maximized
browser display, especially in Firefox.
Probably due to the deep dynamic nesting the height to be displayed
could not be calculated correctly

Define an offset for textarea or textfield during initialization.
This prevents error messages from the linter.

Show warning messages of input fields at event 'NavigationDenied' only
if reason "responsesIncomplete" is sent

- Map value between unit state and element model
- Takes over methods that were previously present in element container
- Gets and holds a list for mapping drop list elements

This prevents the section from being placed in front of elements
with negative z-index

This creates a blockquote-element, which is styled globally with 
specific quotes and alignment.

The inline style makes problems with fixed sized elements in dynamic 
sections.

This change needs to be reviewed thoroughly.

Fix a problem when saving compound children

see https://github.com/iqb-berlin/verona-data-specifications/blob/main/responses/manual_iqb-standard.md

The entire HTML is no longer saved, but only the indices and the color
of the markers

The theme file is now project specific because Angular demands assets
to be part of the project.
It also differs in content: The editor theme is only applied to canvas
elements. For the player every checkbox and radio button is affected.

The components now again use the default color of 'accent'. The custom
theme now has the green as accent color and no longer primary.

- Rename NumbersKeyboardComponent to MathKeyboardComponent
- Decrease the number of input properties
- Split source code into private methods

- Ignore blank pages when calculating the response progress

Add the missing property playerProps

The status of a page is defined by the state of its elements.
Therefore, after restoring the elements, a check of the status of a
page must be triggered.

see Verona Api