Prepare 0.13.0 release

[mtreinish]

This commit prepares the 0.13.0 release. It moves the release notes that for the release to a separate directory and adds a prelude to the release notes. This should be the last commit to merge and after it merges it'll that commit will be tagged as the 0.13.0 release.

TODO:

• Wait for the last PRs in the milestone to merge (or be deferred to the next release)
• Expand some release notes with more detail

[coveralls]

Pull Request Test Coverage Report for Build 5156512620

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 11 unchanged lines in 7 files lost coverage.
• Overall coverage decreased (-0.007%) to 96.47%

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Files with Coverage Reduction	New Missed Lines	%
src/generators.rs	1	98.9%
src/random_graph.rs	1	98.88%
src/shortest_path/all_pairs_dijkstra.rs	1	99.27%
src/shortest_path/mod.rs	1	98.93%
src/centrality.rs	2	93.77%
src/layout/mod.rs	2	97.75%
rustworkx-core/src/connectivity/find_cycle.rs	3	94.34%

Totals
Change from base Build 5145198401:	-0.007%
Covered Lines:	15084
Relevant Lines:	15636

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💛 - Coveralls

[mtreinish]

I decided to defer #823 since it wasn't critical to include in 0.13.0. So with that I think this is unblocked now. So if people are good with the release notes here we can merge this and then tag the release.

[IvanIsCoding]

I decided to defer #823 since it wasn't critical to include in 0.13.0. So with that I think this is unblocked now. So if people are good with the release notes here we can merge this and then tag the release.

I don’t have bandwidth to review it now, but I think we can include it in 0.13.1 before a 0.14 release

I have more Python annotation in the works so we could backport #823 and release 0.13.1 with deferred from release + annotations + fixes if we find bugs