This reverts commit 24dcce7.

01. Added customEmojiFilter helper function that will filter out custom emojis (uploaded to discord server by user). Why: otherwise they're displayed in raw html format, since there're no emojis to translate them to;
02. Added replaceAtWithHash helper function that will filter replace '@' with '#'. Why: '@' is used as an inner reference symbol in Telegram which leads to posts transferred from Discord (if they had any @-mentions in it) to have a lot of unexpected links leading to random channels;
03. Added replaceExcessiveSpaces helper function that will filter out excessive (2 or more) whitespaces from the output. Why: after removing custom emojis html output frequently ends up with excessive spaces;
04. Added removeNewlineSpaces helper function that will filter out whitespaces placed at the beginning of the newline. Why: after removing custom emojis that were placed at the beginning of the newline html output ends up with an unneeded space;