[ENH] Adds issue templates for bugs and discussions (#189)

* Adds bug issue template
Integrates with GitHub's issues template feature. Provides fields for
bug summary, suspected causes and additional details such as OS/Python
version. Can modify by modifying /.github/ISSUE_TEMPLATE/bug_issue.md.
See
https://help.github.com/articles/manually-creating-a-single-issue-template-for-your-repository/
for more information, strategy employed is #3.

* Adds discussion issue template
Adds fields for discussion issue, including summary, goals and
optionally strategy and additional details. For modification notes
reference the previous commmit,
11ca2fe

* Condenses bug and discussion issue templates into one
Per discussions on PR#189, bug and discussions templates are condensed into one general issue template.
Template contains fields for summary, additional detail and next steps.
Co-authored-by: Taylor Salo
Co-authored-by: Elizabeth DuPre

* Adds request to cross-reference related issues

* Alters neurostars submission

* Clarifies context instruction

* Fixes typos in issue template
Addresses comments from
#189 (comment) and
#189 (comment) that
note typos.

* Adds timeline to issue response
Addresses comments at
#189 (comment) which
request a response time guideline, and notes that the issue may not be
resolved right away.

.github/ISSUE_TEMPLATE/issue_template.md

@@ -0,0 +1,45 @@
+---
+name: Issue Template
+about: File an issue
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+<!--
+This is a suggested issue template for tedana.
+
+If there is other information that would be helpful to include, please do not hesitate to add it!
+
+Before submitting, please check to make sure that the issue is not already addressed; if there is a related issue, then please cross-reference it by #.
+If this is a usage question, please check out NeuroStars here:
+https://neurostars.org/
+and tag your topic with "multi-echo"
+-->
+
+<!--
+Summarize the issue in 1-2 sentences, linking other issues if they are relevant
+
+Note: simply typing # will prompt you for open issues to select from
+-->
+### Summary
+
+<!--
+If needed, add additional detail for:
+1. Recreating a bug/problem
+2. Any additional context necessary to understand the issue
+-->
+### Additional Detail
+
+<!--
+If desired, add suggested next steps.
+If you foresee them in a particular order or priority, please use numbering
+-->
+### Next Steps
+
+<!-- 
+Thank you for submitting your issue!
+If you do not receive a response within a calendar week, please post a comment on this issue to catch our attention. 
+Some issues may not be resolved right away due to the volunteer nature of the project; thank you for your patience!
+-->