Lister: add Greek characters to HTML text mode

[Slavic]

In HTML mode, Lister can show some HTML codes like ä as the letters, but currently this list is limited by Latin diacritics. It would be helpful to add the Greek letters to supported characters, like α β etc. Currently their HTML presentation is shown as ordinary text, without interpretation as the letters of Greek alphabet α, β... Greek letters are used in the texts quite often, in science and beyond.

List of entities can be found, for example, here: Entities for Symbols and Greek Letters.