add issue template

.github/ISSUE_TEMPLATE/00-bug.md

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+---
+name: Bugs
+about: config, server, client, or anything else
+title: "affected/package: "
+---
+
+<!--
+Please answer these questions before submitting your issue. Thanks!
+-->
+
+### What version of tnet are you using?
+
+
+### Does this issue reproduce with the latest release?
+
+
+
+### What operating system and processor architecture are you using (`go env`)?
+
+<details><summary><code>go env</code> Output</summary><br><pre>
+$ go env
+
+</pre></details>
+
+### What did you do?
+
+<!--
+If possible, provide a recipe for reproducing the error.
+A complete runnable program is good.
+A link on go.dev/play is best.
+-->
+
+
+### What did you expect to see?
+
+
+
+### What did you see instead?

.github/ISSUE_TEMPLATE/01-feature.md

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+---
+name: Features
+about: config, server, client, or anything else
+title: "affected/package: "
+---
+
+<!--
+Please answer these questions before submitting your issue. Thanks!
+-->
+
+### Is your feature request related to a problem?
+
+<!--
+A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
+-->
+
+### What is the solution you'd like?
+
+<!--
+A clear and concise description of what you want to happen.
+-->
+
+### What alternatives have you considered?
+
+<!--
+A clear and concise description of any alternative solutions or features you've considered.
+-->
+
+### Could you provide additional context?
+
+<!--
+Add any other context or screenshots about the feature request here.
+-->

.github/ISSUE_TEMPLATE/03-proposal.md

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+---
+name: Proposals
+about: New external API or other notable changes
+title: "proposal: affected/package: "
+labels: Proposal
+---
+
+<!--
+Our proposal process is documented here:
+https://github.com/trpc-group/trpc/tree/main/proposal
+-->