Maybe someone can use it:
/* do not show the readme.md file in the list */
tr[data-file*="Readme.md"] {
display: none !important;
}
/* hide the edit menu of the readme.md */
.menubar.autohide{
display: none!important;
}
/* make the "editor field" not clickable */
#editor-wrapper div.ProseMirror[contenteditable="true"],
#editor-wrapper div.ProseMirror[contenteditable="false"] {
pointer-events: none!important;
}
/* give the workspace a fixed height to make it scrollable */
#rich-workspace #editor-container {
height: 250px!important;
}