Add membership request template

Signed-off-by: Kevin Wang <kevinwzf0126@gmail.com>

.github/ISSUE_TEMPLATE/membership-request.md

+---
+name: Membership Request
+about: Request to become a KubeEdge community member
+title: 'REQUEST: New membership for <your name>'
+labels: membership
+assignees: ''
+
+---
+
+## GitHub Username
+<!-- your github handle here -->
+
+## Organization you are requesting membership in
+<!-- The organization name here -->
+
+## Requirements
+
+- [ ] I have reviewed the [community membership guidelines]
+- [ ] I have joined in the community [mailing list] and [slack]
+- [ ] I have enabled [two-factor authentication] on my GitHub account
+- [ ] I am actively contributing to 1 or more KubeEdge subprojects
+- [ ] I have spoken to my sponsors ahead of this application, and they have agreed to sponsor my application
+- [ ] I have checked my affiliation in [devstats] (if it's not correct, please fix in [cncf/gitdm])
+
+## Sponsors
+<!-- List github handle of your sponsors -->
+
+## List of contributions to the KubeEdge project
+- PRs reviewed / authored:
+
+- Issues authored:
+
+- Issues responded to:
+
+[community membership guidelines]: https://github.com/kubeedge/community/blob/master/community-membership.md
+[mailing list]: https://groups.google.com/forum/#!forum/kubeedge
+[slack]: https://kubeedge.slack.com/
+[two-factor authentication]: https://help.github.com/en/github/authenticating-to-github/about-two-factor-authentication
+[devstats]: https://kubeedge.devstats.cncf.io/d/56/company-commits-table?orgId=1
+[cncf/gitdm]: https://github.com/cncf/gitdm#addingupdating-affiliation
+