Add comment templates

[j-f1]

I help triage issues on a repository, and it would be really useful if I could just put /reply duplicate 1234 or /reply repro-steps in a comment and have my comment edited into a helpful response for the OP.

[liuderchi]

@j-f1 that's really awesome idea. It really extends a bot's ability of making templates. Like #5, the most complex part of such feature is design of interpolation of values into a template.

By the time bot can access custom templates from .github, I would implement this feature.

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IMO I would like to keep bot command usage simple, so I would prefer

• always use /template as a directive
• maybe the command would be /template reply_duplicate 1234 then the bot
  • grab .github/REPLY_DUPLICATE.md and replace $1 snippet of the template with 1234
  • comment with generated contents

[liuderchi]

@j-f1 this feature is added in latest release v0.2.0 🎉 You may install it to your repo or try it in #10 playground.