docs: Provide issue/PR templates

To help reduce the number of issues reported against this repository,
this patch provides issue and PR templates, and a support document,
detailing that the repository represents only a metapackage, and that
issue reports and pull requests should be made against the appropriate
component package repository.

.github/ISSUE_TEMPLATE.md

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+** DO NOT OPEN NEW ISSUES ON THIS REPOSITORY **
+
+This repository has not been marked archived/read-only, as we do periodically
+update the list of packages and/or their constraints. However, this repository
+is a _metapackage_, and is only used to install the various packages listed in
+its `composer.json`.
+
+If you find an issue, you should determine which package is responsible, and
+report against the correct package repository. As an example, if you see an
+exception reported that mentions `Zend\Db\Exception\RuntimeException`, this
+indicates an issue with the zend-db package, and should be reported against the
+zendframework/zend-db repository.
+
+In the majority of cases, we will close any new issues without comment.

.github/PULL_REQUEST_TEMPLATE.md

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+** DO NOT OPEN NEW PULL REQUESTS AGAINST THIS REPOSITORY **
+
+This repository has not been marked archived/read-only, as we do periodically
+update the list of packages and/or their constraints. However, this repository
+is a _metapackage_, and is only used to install the various packages listed in
+its `composer.json`.
+
+Only open a pull request that will update existing package constraints; all
+other requests will be closed.

.github/SUPPORT.md

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+# Getting Support
+
+Zend Framework offers the following support channels:
+
+- For real-time questions, use our
+  [chat](https://zendframework-slack.herokuapp.com)
+- For detailed questions (e.g., those requiring examples) use our
+  [forums](https://discourse.zendframework.com/c/questions/components)
+
+**DO NOT** use the issue tracker to ask questions; use chat or the forums for
+that. Questions posed to the issue tracker will be closed.
+
+At this time, this repository has not been marked archived/read-only, as we do
+periodically update the list of packages and/or their constraints. However, this
+repository is a _metapackage_, and is only used to install the various packages
+listed in its `composer.json`. As such, please direct issue reports and patches
+to the appropriate component package repositories.