github: Add preliminary issue templates & configuration.

This adds basic issue templates to support the automatic labelling of
reported issues, and some structure to guide users towards useful
information to report.

This doesn't use forms, much like in the main zulip/zulip repository,
and also supports filing blank issues, since the structure is not
necessary for each case.

Author: neiljp

.github/ISSUE_TEMPLATE/01_crash.md

@@ -0,0 +1,39 @@
+---
+name: Bug report (major)
+about: A major bug which significantly impacts usability, eg. an unexpected quit, crash, freeze.
+labels: 'bug: crash',
+---
+
+### Bug description
+
+
+
+<!-- If discussed in #zulip-terminal or another channel on chat.zulip.org, paste link below: -->
+
+
+### How is the bug triggered?
+How can you reproduce the bug?
+1.
+
+
+### Does it produce a 'traceback' or 'exception'?
+<!-- Copy/paste it between the ``` lines below: -->
+```
+
+
+```
+
+### How are you running the application?
+Please include as many of the following as possible:
+- **Zulip-terminal version:**
+  eg. a specific version (0.7.0), or if running from `main` also ideally the git ref
+- **Zulip server version(s):**
+  eg. Zulip Cloud, the version you are running self-hosted, or the Zulip Community server (chat.zulip.org)
+- **Operating system (and version):**
+  eg. Debian Linux, Ubuntu Linux, macOS, WSL in Windows, Docker
+- **Python version (and implementation):**
+  eg. 3.8, 3.9, 3.10, ... (implementation is likely to be eg. CPython, or PyPy)
+
+If possible, please provide details from the `About` menu: (hotkey: Meta + ?)
+(this can provide some of the details above)
+

.github/ISSUE_TEMPLATE/02_bug.md

@@ -0,0 +1,36 @@
+---
+name: Bug report
+about: A concrete bug report with steps to reproduce the behavior.
+labels: bug,
+---
+
+### Bug description
+
+
+
+<!-- If discussed in #zulip-terminal or another channel on chat.zulip.org, paste link below: -->
+
+
+### How is the bug triggered?
+How can you reproduce the bug?
+1.
+
+
+### What did you expect to happen?
+
+
+
+### How are you running the application?
+Please include as many of the following as possible:
+- **Zulip-terminal version:**
+  eg. a specific version (0.7.0), or if running from `main` also ideally the git ref
+- **Zulip server version(s):**
+  eg. Zulip Cloud, the version you are running self-hosted, or the Zulip Community server (chat.zulip.org)
+- **Operating system (and version):**
+  eg. Debian Linux, Ubuntu Linux, macOS, WSL in Windows, Docker
+- **Python version (and implementation):**
+  eg. 3.8, 3.9, 3.10, ... (implementation is likely to be eg. CPython, or PyPy)
+
+If possible, please provide details from the `About` menu: (hotkey: Meta + ?)
+(this can provide some of the details above)
+

.github/ISSUE_TEMPLATE/03_parity.md

@@ -0,0 +1,25 @@
+---
+name: Feature request (a missing known Zulip feature)
+about: A request for a feature which is missing, but present in another Zulip client (eg. Web/Desktop/mobile).
+labels: 'missing feature',
+---
+
+### Description of feature missing from another Zulip client
+<!-- Is this an entire missing feature? Or part of the feature? -->
+
+
+
+<!-- If discussed in #zulip-terminal or another channel on chat.zulip.org, paste link below: -->
+
+
+### When was this feature first available in Zulip?
+If you know:
+- **Zulip version:**
+  (eg. 2.1, 5.0, 8.0, ..., or 'Zulip Cloud today')
+- **Zulip feature level:**
+  (see https://zulip.com/api/changelog)
+
+
+### Other details
+
+

.github/ISSUE_TEMPLATE/04_platform.md

@@ -0,0 +1,19 @@
+---
+name: Feature suggestion
+about: A suggestion for an improvement, specific to the capabilities of the terminal environment.
+labels: enhancement,
+---
+
+<!--
+NOTE: If your proposed feature:
+1) is already available in Zulip, please use the other issue feature category
+2) would be of benefit to Zulip clients generally, please instead report it at:
+   https://github.com/zulip/zulip/issues/new/choose
+-->
+
+### Description of suggested feature
+
+
+
+<!-- If discussed in #zulip-terminal or another channel on chat.zulip.org, paste link below: -->
+

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,8 @@
+blank_issues_enabled: true
+contact_links:
+  - name: Report broader Zulip issues (beyond Zulip-Terminal)
+    about: Includes links to best-practices for filing bug reports, feature requests, security vulnerabilities and more.
+    url: https://github.com/zulip/zulip/issues/new/choose
+  - name: Not sure?
+    about: 'Chat with us, using any of the Zulip clients, in #zulip-terminal on the Developer Community server (chat.zulip.org).'
+    url: https://zulip.com/development-community