Add Raspberry/epd to .gitignore

[abhillman]

Before:

% git status
HEAD detached at 8640693
Untracked files:
  (use "git add <file>..." to include in what will be committed)
	epd

After:

% ls -la epd
-rw-r--r--  1 abhillman  staff  0 Apr 17 16:51 epd
% git status
On branch abhillman/add-epd-to-gitignore
Your branch is up to date with 'origin/abhillman/add-epd-to-gitignore'.

nothing to commit, working tree clean

cc/ @shhds @waveshare