Emma Corrin has boarded “Post,” a new short film directed by Alice Wordsworth and written by Flora Ashton, as an executive producer. Described as a “stylized, darkly comic and simmering” story, “Post” centers on “the brewing storm of a fiercely lonely woman demanding to be seen,” according to its synopsis, and “invites us to look again at the strangers we pass each day.” Alongside Corrin as executive producer, “Post” has announced its main cast: BAFTA nominee Omari Douglas (“Black Doves,” “It’s