[Documentation] Move all wiki pages into the repo and make it pretty (#2494)

docs/08_Format_API/03_FormatAbstract.md

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+The `FormatAbstract` class implements the [`FormatInterface`](../08_Format_API/02_FormatInterface.md) interface with basic functional behavior and adds common helper functions for new formats:
+
+* [setContentType](#the-setcontenttype-function)
+* [callContentType](#the-callcontenttype-function)
+* [sanitizeHtml](#the-sanitizehtml-function)
+* [array_trim](#the-array_trim-function)
+
+# Functions
+
+## The `setContentType` function
+
+The `setContentType` function receives a string defining the content type for the HTML header and must return the object instance.
+
+```PHP
+setContentType(string): self
+```
+
+## The `callContentType` function
+
+The `callContentType` function applies the content type to the header data and must return the object instance.
+
+```PHP
+callContentType(): self
+```
+
+## The `sanitizeHtml` function
+
+The `sanitizeHtml` function receives an HTML formatted string and returns the string with disabled `<script>`, `<iframe>` and `<link>` tags.
+
+```PHP
+sanitizeHtml(string $html): string
+```
+
+## The `array_trim` function
+
+The `array_trim` function receives an array of strings and returns the same array with all elements trimmed (like using the `trim` function on all elements)
+
+```PHP
+array_trim(array $elements): array
+```