Add https upgrade readme (#3690)

Task/Issue URL:
https://app.asana.com/0/488551667048375/1205687772894384/f

### Description
Adds a readme for the https upgrade module.

Author: joshliebe

httpsupgrade/readme.md

@@ -0,0 +1,9 @@
+# HTTPS Upgrade
+Https, or Smart Encryption, tries to upgrade http requests to https efficiently using the bundled bloom filter.
+
+## Who can help you better understand this feature?
+- Marcos Holgado
+- Cristian Monforte
+
+## More information
+- [Asana: Known Issues (Improve Downloads)](https://app.asana.com/0/0/1200925594468359/f)