[blog] Add blog on Pulsar Summit CFP (apache#5888)

### Motivation
Pulsar Summit CFP is open, we need a blog to announce it.

### Modifications
Add a blog to announce Pulsar Summit CFP.

site2/website/blog/2019-12-18-Pulsar-summit-cfp.md

@@ -0,0 +1,43 @@
+---
+author: Jennifer Huang  
+authorURL: https://twitter.com/Jennife06125739  
+title: Pulsar Summit San Francisco 2020 CFP is now open
+
+---
+
+Pulsar Summit is an annual conference dedicated to Apache Pulsar community, bringing together an international audience of CTOs/CIOs, developers, data architects, data scientists, Apache Pulsar committers/contributors, and the messaging and streaming community, to share experiences, exchange ideas and knowledge about Pulsar and its growing community, and receive hands-on training sessions led by Pulsar experts.
+
+We are excited to announce that the first Pulsar Summit will be held in San Francisco in April, 2020. Talk submissions, pre-registration, and sponsorship opportunities are now open for the conference!
+
+## Speak at Pulsar Summit
+Presentations and lightning talks are accepted for speaking proposals. Suggested topics cover Pulsar use cases, operations, technology deep dive, and ecosystem. Submissions are open until **January 31, 2020**.
+
+If you are unsure about your proposal, or want some feedback or advice in general, please do not hesitate to reach out to [[email protected]](mailto:[email protected]). We are happy to help out! Further details are available on the [CFP website](https://pulsar-summit.org/call-for-presentations/).
+
+## Dates to remember
+- CFP opens: December 15, 2019
+- CFP closes: January 31, 2020 - 23:59 PST
+- CFP notification: February 21, 2020
+- Schedule announcement: February 24, 2020
+
+## Speaker benefits
+When your speaking proposal is approved, you will enjoy the following benefits:
+
+- Full conference pass.
+- Exclusive swag only available to speakers.
+- Expand your network and raise your profile in the Pulsar community.
+- A professionally produced video of your presentation.
+- Your name, title, company, and bio will be featured on the Pulsar Summit San Francisco 2020 website.
+- Your session will be added to the Pulsar Summit YouTube Channel and promoted on Twitter and LinkedIn.
+
+## Pre-registration
+If you are interested in attending Pulsar Summit San Francisco 2020, we’d like to hear from you with your [pre-registration](https://pulsar-summit.org/pre-registration/). Your ideas are very important to us, and we will prepare the content accordingly. 
+
+After you submit the pre-registration form, you will be added to the waitlist of Pulsar Summit San Francisco 2020. Once the registration is open, you will be notified with an email.
+
+## Sponsor Pulsar Summit
+Pulsar Summit is a community run conference and your support is needed. Sponsoring this event will provide a great opportunity for your organization to further engage with the Apache Pulsar community. [Contact us](mailto:[email protected]) to learn more.
+
+Help us make #PulsarSummit 2020 a big success by spreading the word and submitting your proposal! Follow us on Twitter ([@pulsarsummit](https://twitter.com/PulsarSummit)) to receive the latest updates of the conference!
+
+Hope to see you at Pulsar Summit San Francisco 2020!