.github: Add ISSUE_TEMPLATE.md

Content of file ISSUE_TEMPLATE.md lossly based upon
e38fcc3c00/.github/ISSUE_TEMPLATE.md

Signed-off-by: Christoffer <netravnen@gmail.com>

.github/ISSUE_TEMPLATE.md

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+### How to submit issue
+Please use this text as a template and replace text in the sections or remove
+the entire section if that does not apply to your issue. For example in case of
+question or feature request, just description with some example is probably
+fine. Also remember to use github's markup form properly, especially in case of
+output or code listing.
+
+### Things you may try first
+(put "x" in "[]" if you already tried following)
+* [] Did you check if this is a duplicate issue?
+* [] Did you test it on the latest FRRouting/frr master branch?
+
+**Related Issue:**
+[fill here if applicable]
+
+### Description
+[Description of the bug or feature]
+
+### Steps to Reproduce
+1. [First Step]
+2. [Second Step]
+3. [and so on...]
+
+**Expected behavior:**
+ [What you expected to happen]
+
+**Actual behavior:**
+ [What actually happened]
+
+### Components:
+[bgpd, build, doc, isisd, ospfd, etc.]
+
+### Attachments
+[Attach if applicable. Fx. log-files, log-lines. etc. etc.]
+
+You're also welcomed to provide us with any other data you think may be useful.
+
+Thanks!