Create basic issue template (#4107)

* Create basic issue template

* Update ISSUE_TEMPLATE.md

ISSUE_TEMPLATE.md

+Thank you for submitting an issue!
+
+Please make sure you include the names of the affected language(s), compiler version(s), operating system version(s), and FlatBuffers version(s) in your issue title.
+
+This helps us get the correct maintainers to look at your issue. Here are examples of good titles:
+
+- Crash when accessing FlatBuffer [C++, gcc 4.8, OS X, master]
+- Flatc converts a protobuf 'bytes' field to 'string' in fbs schema file [all languages, FlatBuffers 1.4]
+
+Include other details as appropriate.
+
+Thanks!