This changes parseDescription to properly encode things to be safe for
usage without removing things like backslashes that may be relevant.
* text.SanitizePlaintext already calls html.UnescapeString so we don't
have to do that
* Replace \n with space early
* Remove duplicate white-space by splitting on fields and joining
* HTML-escape the string we have
* For extra certainty, encode the backslash as \
Fixes#1549
* f0x gitignore additions
* better meta title and descriptions
* user avatar icon for thread and profile meta tags
* use proper tag for image
* whitespace
* add noescapeAttr template function
* use ogMeta struct for opengraph
* maxOGDescriptionLength = 300
Co-authored-by: tsmethurst <tobi.smethurst@protonmail.com>