Add electromagnetism summary

It contains a summary of topics 1 through 4.

Change-Id: Id41a440f77d5b3c2ae52a10c3db1b5314bc8d777
diff --git a/quad8/electro/resum/.gitignore b/quad8/electro/resum/.gitignore
new file mode 100644
index 0000000..a136337
--- /dev/null
+++ b/quad8/electro/resum/.gitignore
@@ -0,0 +1 @@
+*.pdf