Add docs for writing announcements.

README.md

@@ -2,6 +2,57 @@
 
 Canonical source for Mozilla Foundation Security Advisories. http://www.mozilla.org/security/announce/
 
+## Writing new announcements
+
+Announcements are written in [Markdown](http://daringfireball.net/projects/markdown/basics). They should
+be named in the pattern `announce/YYYY/mfsaYYYY-XX.md` where `YYYY` is the 4 digit year, and `XX` is
+the next in the sequence. Once the file is created some data about the file should be added to the
+[Front Matter](http://jekyllrb.com/docs/frontmatter/). Front Matter is [YAML](http://yaml.org/spec/1.1/)
+encoded data surrounded by lines containing 3 dashes. Then the Markdown content can be added below the 
+Front Matter. For example:
+
+```markdown
+---
+announced: April 29, 2014
+fixed_in:
+- Firefox 29
+- Firefox ESR 24.5
+- Thunderbird 24.5
+- Seamonkey 2.26
+impact: High
+mfsa_id: 2014-38
+reporter: Abhishek Arya
+title: Buffer overflow when using non-XBL object as XBL
+---
+
+### Description
+
+Mozilla community member **James Kitchener** reported a crash in
+DirectWrite when rendering MathML content with specific fonts due to an error in
+how font resources and tables are handled. This leads to use-after-free of a
+DirectWrite font-face object, resulting in a potentially exploitable crash.
+```
+
+> **NOTE:** HTML is valid Markdown. So if you need extra features or classes, just add them.
+
+### Metadata spec
+
+There are some required elements in the Front Matter data (metadata). They are:
+
+```yaml
+announced: Date in Month Day, Year format
+fixed_in: List of product names and versions (see example above)
+impact: one of (Critical, High, Moderate, Low)
+mfsa_id: YYYY-XX (same as file name)
+reporter: Name of bug reporter
+title: Title of the advisory (may contain HTML).
+```
+
+Other data will be displayed, but the above will be expected in the template and styled correctly.
+
+> **NOTE:** You should *NOT* add a `products:` section to the data. The list of products is extracted
+> from the `fixed_in:` list when imported into the website.
+
 ## Import Script
 
 `import_html.py` is a script that will convert the Mozilla Foundation Security Announcement HTML (PHP) files from [the SVN repository](http://svn.mozilla.org/projects/mozilla.org/trunk/security/) into markdown snippets suitable for inclusion in [bedrock](https://github.com/mozilla/bedrock/) (the new backend for www.mozilla.org).