Release empty Rack 2 compatible version.

[lsylvester]

As per the suggestion at rack/rack#1805 (comment) - it would be good to have a version of rack-session that is compatible with rack 2.0.

In particular - I am looking at how Sidekiq can relax its dependency on rack to allow for upgrading to rack 3. While rack-session is only compatible with rack >= 3.0 - we are not able to add rack-session as a dependency so that it can be included in all of the applications.

By providing an empty rack-session gem that is compatible with rack 2 - we allow gems to specify a dependency on rack-session and maintain compatibility with rack 2 and 3 transparently to the application developers.

I have prepared a branch that I think should be able to be used to build and publish a v0.1.1 version of the gem at main...lsylvester:rack-session:v0.1.1 (I have not made this as a PR as it should not be merged).

[dentarg]

@ioquatix this sounds like a good idea (I know we touched on it over at sinatra/sinatra) although I don't have a particular use-case for it right now (haven't found the opportunity to dive into trying to make Sinatra work with Rack 3)

[ioquatix]

Okay, v1 release of rack-session will be for rack < 3, and v2 release will be for rack 3+.

[ioquatix]

Okay this is all released. v1.0.0 is Rack < 3 and v2.0.0 is Rack >= 3.

[ioquatix]

The same is now also true for the rackup gem.

[pboling]

The README for stable-v1 branch, and shipping in the actual v1 gem, is incorrectly telling people to add require "rack/session", which will blow up since that file doesn't exist in either the rack v2 gem or the rack-session v1 gem. Reported as #27.