About igraph releases and other things

A new maintenance release of IGraph/M is now available. This is a bugfix release recommended for all users. As usual, the simplest way to upgrade is to evaluate the following, and then restart Mathematica:

```
Get["https://raw.githubusercontent.com/szhorvat/IGraphM/master/IGInstaller.m"]
```

Changed:

- When an invalid vertex is passed to IGraph/M functions, now the message shown is
`IGraphM::invv`

instead of`VertexIndex::inv`

.

Fixed:

- In rare cases, vertex names that were lists of other vertex names in the same graph were misinterpreted. This affected only Mathematica 12.0 and later.
`IGCommunitiesLeadingEigenvector`

is less likely to fail to converge now.`IGCommunitiesLeadingEigenvector`

now respects random seeds set in Mathematica. These affect only the random starting vector it uses internally, which can very rarely cause non-deterministic output.`IGBarabasiAlbertGame`

no longer accepts negative or zero exponents, as these were not handled correctly.`IGBridges`

is no longer prone to stack overflow when given very large graphs.

Other:

- Performance improvements for
`IGGraphEditor`

. - Documentation improvements.