Quick improvements and fixes to run Spyder on Binder

[ccordoba12]

Our Binder integration is broken or semi-broken right now. In yesterday's developer meeting we agreed to do the following quick steps to improve it:

• Update spyder-stable branch in Binder-environments - https://github.com/spyder-ide/binder-environments/tree/61157cebbabfb15825a96497f16bc0d2afaea155
• Update our docs to point to that branch- PR Update binder link to point to the current stable version spyder-docs#336
• Add a new section to our Readme with a launch|binder button to that branch and remove the current button - PR PR: Update binder link and add instructions when releasing new versions to keep it updated #19936
• Add a new instruction to our release instructions so that we don't forget to update our Binder images after each release - PR: Update binder link and add instructions when releasing new versions to keep it updated #19936

spyder-stable branch binder link: https://mybinder.org/v2/gh/spyder-ide/binder-environments/spyder-stable?urlpath=git-pull%3Frepo%3Dhttps%253A%252F%252Fgithub.com%252Fspyder-ide%252FSpyder-Workshop%26urlpath%3Ddesktop%252F%26branch%3Dmaster

[dalthviz]

Should we merge #19750 before proceding with the Binder-environments branch update @ccordoba12 ?

[ccordoba12]

Good idea, please do @dalthviz.

[dalthviz]

Done 👍