[GitHub] Tweak PR and issue templates (sonic-net#1419)

Tweak GitHub issue and pull request templates

- Rename files to align with new standard
- Use markdown headings rather than bolded bullets

Author: jleveque

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,60 @@
+<!--
+    If you are reporting a new issue, make sure that we do not have any duplicates
+    already open. You can ensure this by searching the issue list for this
+    repository. If there is a duplicate, please close your issue and add a comment
+    to the existing issue instead.
+
+    If you suspect your issue is a bug, please edit your issue description to
+    include the BUG REPORT INFORMATION shown below. If you fail to provide this
+    information within 7 days, we cannot debug your issue and will close it. We
+    will, however, reopen it if you later provide the information.
+
+    For more information about reporting issues, see
+    https://github.com/Azure/SONiC/wiki#report-issues
+
+    ---------------------------------------------------
+    GENERAL SUPPORT INFORMATION
+    ---------------------------------------------------
+
+    The GitHub issue tracker is for bug reports and feature requests.
+    General support can be found at the following locations:
+
+    - SONiC Support Forums - https://groups.google.com/forum/#!forum/sonicproject
+
+    ---------------------------------------------------
+    BUG REPORT INFORMATION
+    ---------------------------------------------------
+    Use the commands below to provide key information from your environment:
+    You do NOT have to include this information if this is a FEATURE REQUEST
+-->
+
+#### Description
+
+<!--
+     Briefly describe the problem you are having in a few paragraphs.
+-->
+
+## Steps to reproduce the issue
+1.
+2.
+3.
+
+#### Describe the results you received
+
+
+#### Describe the results you expected
+
+
+#### Additional information you deem important (e.g. issue happens only occasionally)
+
+
+#### Output of `show version`
+
+```
+(paste your output here)
+```
+
+<!--
+     Also attach debug file produced by `sudo generate_dump`
+-->
+

.github/PULL_REQUEST_TEMPLATE.md

@@ -0,0 +1,32 @@
+<!--
+    Please make sure you've read and understood our contributing guidelines:
+    https://github.com/Azure/SONiC/blob/gh-pages/CONTRIBUTING.md
+
+    ** Make sure all your commits include a signature generated with `git commit -s` **
+
+    If this is a bug fix, make sure your description includes "closes #xxxx",
+    "fixes #xxxx" or "resolves #xxxx" so that GitHub automatically closes the related
+    issue when the PR is merged.
+
+    If you are adding/modifying/removing any command or utility script, please also
+    make sure to add/modify/remove any unit tests from the tests
+    directory as appropriate.
+
+    If you are modifying or removing an existing 'show', 'config' or 'sonic-clear'
+    subcommand, or you are adding a new subcommand, please make sure you also
+    update the Command Line Reference Guide (doc/Command-Reference.md) to reflect
+    your changes.
+
+    Please provide the following information:
+-->
+
+#### What I did
+
+#### How I did it
+
+#### How to verify it
+
+#### Previous command output (if the output of a command-line utility has changed)
+
+#### New command output (if the output of a command-line utility has changed)
+