[workflow] Update issue templates

.github/ISSUE_TEMPLATE/bug_report.md

@@ -13,9 +13,24 @@ assignees: ''
 A clear and concise description of what the bug is, ideally within 20 words.
 
 **To Reproduce**
-Please post a sample code to reproduce the bug. The developer team will put a higher priority on bugs that can be reproduced within 20 lines of code. If you want a prompt reply, please keep the code short.
+Please post a **minimal sample code** to reproduce the bug.
+The developer team will put a higher priority on bugs that can be reproduced within 20 lines of code. If you want a prompt reply, please keep the sample code **short** and **representative**.
+
+```py
+# sample code here
+```
 
 **Log/Screenshots**
-Please post the full log of the program (instead of just a few lines around the error message, unless the log is > 1000 lines). This will help us diagnose what's happening.
+Please post the **full log** of the program (instead of just a few lines around the error message, unless the log is > 1000 lines). This will help us diagnose what's happening. For example:
+
+```
+$ python my_sample_code.py
+[Taichi] mode=release
+[Taichi] version 0.6.29, llvm 10.0.0, commit b63f6663, linux, python 3.8.3
+...
+```
+
+**Additional comments**
+If possible, please also consider attaching the output of command `ti diagnose`. This produces the detailed environment information and hopefully helps us diagnose faster.
 
-**If you have local commits (e.g. compile fixes before you reproduce the bug), please make sure you first make a PR to fix the build errors and then report the bug.**
+If you have local commits (e.g. compile fixes before you reproduce the bug), please make sure you first make a PR to fix the build errors and then report the bug.

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,9 @@
+# Ref: https://github.com/pypa/pypi-support/blob/master/.github/ISSUE_TEMPLATE/config.yml
+blank_issues_enabled: true
+contact_links:
+  - name: Contributor Guideline
+    url: https://taichi.readthedocs.io/en/latest/contributor_guide.html
+    about: Please check this out if you'd like to contribute by opening a PR :)
+  - name: Taichi Forum
+    url: https://forum.taichi.graphics
+    about: GitHub issues too formal? Questions about Taichi? Feel free to chat on our forum!

.github/ISSUE_TEMPLATE/feature_request.md

@@ -8,7 +8,7 @@ assignees: ''
 ---
 
 **Concisely describe the proposed feature**
-A clear and concise description of what you want. For example, 
+A clear and concise description of what you want. For example,
 > I would like to add an Apple Metal backend to the compiler so that my Macbook GPU can be utilized.
 
 **Describe the solution you'd like (if any)**

.github/pull_request_template.md

@@ -1,3 +1,5 @@
+Related issue = #
+
 <!--
 Thanks for your PR!
 If it's your first time contributing to Taichi, please make sure you have read our Contributor Guideline:
@@ -16,7 +18,6 @@ If it's your first time contributing to Taichi, please make sure you have read o
 - So that when the PR gets merged, GitHub will **automatically** close the issue #2345 for you.
 - If the PR doesn't belong to any existing issue, and it's a trivial change, feel free to leave it blank :)
   -->
-Related issue = #
 
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