Issue template added.

.github/ISSUE_TEMPLATE.md

@@ -0,0 +1,38 @@
+<!--
+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.
+
+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:**
+
+
+**Output of `go version`:**
+
+```
+(paste your output here)
+```
+
+**Excelize version or commit ID:**
+
+```
+(paste here)
+```