initialize readme

README.md

+# my-certificate-alert
+
+A very basic program that sits and listens for new certificates to be issued.
+If any certificates match a list of domains, send a Pushover notification.
+
+## Configuring
+
+This reads a few environment variables:
+
+|Name|Description|
+|:--|----|
+|`MCA_DOMAINS_LIST`|A plain text, `\n` delineated file that lists the domains to send an alert for.|
+|`MCA_PUSHOVER_USER_KEY`|Your personal user API key.|