Escape the value according to the RFC2445 rules.
A double quote becomes \"; a comma becomes \,; a colon
becomes ":"; a semicolon becomes \;; a backslash becomes
\\ and a newline becomes \n.
It is also ensures that any single line is maximum 70 characters long by splitting the lines with newline/space combinations.
For example:
{{ value|escape_ical }}When the value is abc:d;e then the output is abc":"d\;e.
.. seealso:: :ref:`filter-escape`