docs(dateFilter): add example of string literals in format string
docs(dateFilter): add example of string literals in format string

Also changes the wording to include the word "escaped" and "escape", which may help users find the
information they're looking for via searching. (ﾉ◕ヮ◕)ﾉ*:･ﾟ✧

Closes #8770

ggershoni/angular.js,ggershoni/angular.js,ggershoni/angular.js,ggershoni/angular.js