community: add discussions and community chat in issue template

[skyzh]

What's changed and what's your intention?

As title. We prefer to use issue to track bugs and features.

Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests

Refer to a related PR or issue link (optional)

[codecov]

Codecov Report

Merging #1741 (b5ffa6d) into main (3f5f703) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1741      +/-   ##
==========================================
- Coverage   71.29%   71.29%   -0.01%     
==========================================
  Files         599      599              
  Lines       77672    77672              
==========================================
- Hits        55377    55373       -4     
- Misses      22295    22299       +4     

Flag	Coverage Δ
rust	71.29% <ø> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
src/connector/src/filesystem/file_common.rs	80.35% <0.00%> (-0.45%)	⬇️
.../src/executor/managed_state/aggregation/extreme.rs	90.13% <0.00%> (-0.28%)	⬇️
src/common/src/types/ordered_float.rs	23.50% <0.00%> (-0.20%)	⬇️

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