Enable Markdown support in display of skill description in Skill Manager Gui

CC @dreher

After:

There is a splitter between the description and the arguments tree, so you can reduce the description's size if necessary.

source/RobotAPI/gui-plugins/SkillManagerPlugin/aronTreeWidget/widgets/SkillDescriptionWidget.cpp

+#include "SkillDescriptionWidget.h"
+
+#include <sstream>
+
+#include <QGridLayout>
+#include <QLabel>
+#include <QTextEdit>
+
+#include <ArmarXGui/libraries/ArmarXGuiBase/widgets/cpp-markdown/markdown.h> // ToDo: Move cpp-markdown to own Axii module.
+
+namespace armarx
+{
+
+    static std::string
+    markdownToHtml(const std::string& markdownText, size_t spacesPerTab = 2)
+    {
+        ::markdown::Document document(spacesPerTab);
+        document.read(markdownText);
+
+        std::stringstream html;
+        document.write(html);
+        return html.str();
+    }
+
+    SkillDescriptionWidget::SkillDescriptionWidget(QWidget* parent) : QWidget{parent}
+    {
+        QGridLayout* layout = new QGridLayout;
+        setLayout(layout);
+
+        layout->setMargin(0);
+
+        int row = 0;
+        int col = 0;
+
+        layout->addWidget(new QLabel("Name:"), row, col++);
+        name = new QLabel;
+        layout->addWidget(name, row, col++);
+
+        // Add some padding.
+        layout->addWidget(new QLabel(), row, col++);
+
+        {
+            QLabel* label = new QLabel("Timeout:");
+            label->setAlignment(Qt::AlignmentFlag::AlignRight);
+            layout->addWidget(label, row, col++);
+        }
+        timeout = new QLabel;
+        timeout->setAlignment(Qt::AlignmentFlag::AlignRight);
+        layout->addWidget(timeout, row, col++);
+
+        ++row;
+        int numCols = col;
+        col = 0;
+
+        description = new QTextEdit;
+        description->setReadOnly(true);
+        layout->addWidget(description, row, col, 1, numCols);
+        ++row;
+    }
+
+    void
+    SkillDescriptionWidget::setSkillDescription(const skills::SkillDescription& desc)
+    {
+        name->setText(QString::fromStdString(desc.skillId.skillName));
+        description->setHtml(QString::fromStdString(markdownToHtml(desc.description)));
+
+        std::stringstream timeoutStr;
+        timeoutStr << desc.timeout;
+        timeout->setText(QString::fromStdString(timeoutStr.str()));
+    }
+
+} // namespace armarx