Function generate_html_for_char 

fn generate_html_for_char(
    uch: char,
    attributes: &LincolnState,
    _advance: bool,
) -> String

Generate HTML corresponding to Lincoln Writer character (in the given state).

While currently we use sup/sub elements here, this does not quite correspond with the way the Lincoln Writer generated superscript/subscript letters. For the LW, these corresponded to half-line movements of the platen (see pages 9-11) of “The Lincoln Writer” (Lincoln Lab Group Report 51-8).

Also, the “line feed up” and “line feed down” characters don’t affect the script in effect. Per page 10 of “The Lincoln Writer” (i.e. the same document mentioned above):

The line feed selectors do not affect the last remembered script position of the typewriter. Therefore after one or more line feed selections, care must be taken to return the typewriter platen to its original position by the selection of the opposite line feed. For example, if the typewriter platen were in normal script position and a line feed-up were selected - followed by printable characters, the printed result would be the same as if a superscript had been selected. However, if this were to be followed by a normal script selection there would be no change since the typewriter would act as if it was already in normal script, (since no other script had been selected). Consequently the line feed selections should be used for situations like superscripting a superscript or subscripting a subscript, etc. On these occasions the opposite line feed should be used to return the typewriter to its original script position.