Add proposed security policy (#1803)

* Add proposed security policy

Signed-off-by: Eric Reinecke <ereinecke@netflix.com>

* Updated dependencies in security policy to cover python vs. C++. Added SECURITY.md to MANIFEST.in

Signed-off-by: Eric Reinecke <ereinecke@netflix.com>

* Added MIT license URL to linkcheck ignore due to 403 when attempted from github runner

Signed-off-by: Eric Reinecke <ereinecke@netflix.com>

* Updated SECURITY.md to include 0.18.x

Signed-off-by: Eric Reinecke <ereinecke@netflix.com>

---------

Signed-off-by: Eric Reinecke <ereinecke@netflix.com>

Author: reinecke

MANIFEST.in

@@ -1,4 +1,4 @@
-include README.md README_contrib.md CHANGELOG.md LICENSE.txt NOTICE.txt CMakeLists.txt
+include README.md README_contrib.md CHANGELOG.md LICENSE.txt NOTICE.txt SECURITY.md CMakeLists.txt
 recursive-include examples *
 recursive-include src *
 recursive-include tests *

SECURITY.md

@@ -0,0 +1,56 @@
+<!-- SPDX-License-Identifier: Apache-2.0 -->
+<!-- Copyright Contributors to the OpenTimelineIO project -->
+
+# Security Policy
+
+## Reporting a Vulnerability
+
+If you think you've found a potential vulnerability in OpenTimelineIO, please
+report it by filing a GitHub [security
+advisory](https://github.com/AcademySoftwareFoundation/OpenTimelineIO/security/advisories/new). Alternatively, email
+[security@opentimeline.io](mailto:security@opentimeline.io?subject=OpenTimelineIO%20Vulnerability%20Report&body=Impact%0A_What%20is%20it,%20who%20is%20impacted_%0A%0APatches%0A_Has%20it%20been%20patched%20and%20in%20which%20version_%0A%0AWorkarounds%0A_Is%20there%20a%20way%20for%20users%20to%20fix%20or%20remediate%20without%20upgrading_%0A%0AReferences%0A_Where%20can%20users%20visit%20to%20find%20out%20more_)
+and provide your contact info for further private/secure discussion.  If your email does not receive a prompt
+acknowledgement, your address may be blocked.
+
+Our policy is to acknowledge the receipt of vulnerability reports
+within 48 hours. Our policy is to address critical security vulnerabilities
+rapidly and post patches within 14 days if possible.
+
+## Known Vulnerabilities
+
+These vulnerabilities are present in the given versions:
+
+* No known vulnerabilities
+
+See the [release notes](https://github.com/AcademySoftwareFoundation/OpenTimelineIO/releases) for more information.
+
+## Supported Versions
+
+This gives guidance about which branches are supported with patches to
+security vulnerabilities.
+
+| Version / branch | Supported                                                                                                                          |
+|------------------|------------------------------------------------------------------------------------------------------------------------------------|
+| main             | :white_check_mark: :construction: ALL fixes immediately, but this is a branch under development and may be unstable in other ways. |
+| 0.18.x           | :white_check_mark: All fixes that can be backported without breaking compatibility.                                            |
+| 0.17.x           | :white_check_mark: All fixes that can be backported without breaking compatibility.                                            |
+| 0.16.x           | :warning: Only the most critical fixes, only if they can be easily backported.                                                     |
+| <= 0.15.x        | :x: No longer receiving patches of any kind.                                                                                       |
+
+  
+### Software Dependencies
+
+#### OpenTimelineIO C++
+
+- [Imath](https://github.com/AcademySoftwareFoundation/Imath) - Provides Vector, Matrix, and Bounding Box primitives. 
+- [rapidjson](https://github.com/Tencent/rapidjson/) - Used in serialization/deserialization of the `.otio` JSON file format.
+
+#### OpenTimelineIO Python
+
+- [pybind11](https://github.com/pybind/pybind11) (only if built with Python bindings) - Used to create Python bindings for the C++ library.
+- [importlib_metadata](https://pypi.org/project/importlib-metadata/) - Provides backward compatability for Python 3.7.
+
+Optionally, OTIOView requires:
+
+- [PySide2](https://pypi.org/project/PySide2/) - on x86_64.
+- [PySide6](https://pypi.org/project/PySide6/) - on AArch64.