feat: add psd export support

[antipalindrome]

• support psd export
  • closes [REQUEST] add export to PSD option #92
• add additional string substitution
  • closes full naming controll #71

New string substitutions:

Option	Example
{ln}	Will be replaced with the layer name. Useful for when exporting filenames as their index
{dn}	Will be replaced with the document name
{M}	Will be replaced with the month
{MM}	Will be replaced with the month, with a leading zero
{D}	Will be replaced with the date of the month
{DD}	Will be replaced with the date of the month, with a leading zero
{YY}	Will be replaced with the year, as the last two digits
{YYYY}	Will be replaced with the year, as all four
{HH}	Will be replaced with the hours, with a leading zero
{mm}	Will be replaced with the minutes, with a leading zero
{ss}	Will be replaced with the seconds, with a leading zero
{sss}	Will be replaced with the milliseconds, with leading zeros