.github: add link to questions in ISSUE_TEMPLATE

[seankhliao]

Add a link redirecting questions to the wiki page/forums

[gopherbot]

This PR (HEAD: a927ce5) has been imported to Gerrit for code review.

Please visit https://go-review.googlesource.com/c/go/+/213440 to see it.

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See the Wiki page for more info

[gopherbot]

Message from Gobot Gobot:

Patch Set 1:

Congratulations on opening your first change. Thank you for your contribution!

Next steps:
Within the next week or so, a maintainer will review your change and provide
feedback. See https://golang.org/doc/contribute.html#review for more info and
tips to get your patch through code review.

Most changes in the Go project go through a few rounds of revision. This can be
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During May-July and Nov-Jan the Go project is in a code freeze, during which
little code gets reviewed or merged. If a reviewer responds with a comment like
R=go1.11, it means that this CL will be reviewed as part of the next development
cycle. See https://golang.org/s/release for more details.

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Please don’t reply on this GitHub thread. Visit golang.org/cl/213440.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

Message from Brad Fitzpatrick:

Patch Set 1: Code-Review+2

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Please don’t reply on this GitHub thread. Visit golang.org/cl/213440.
After addressing review feedback, remember to publish your drafts!

[gopherbot]

This PR is being closed because golang.org/cl/213440 has been merged.