Rename master branch to 1.x and update installation instructions

[clue]

Builds on top of #166
Refs reactphp/async#29

[llaville]

@clue Don't forget to update also https://github.com/graphp/graphviz/blob/master/composer.json#L13 to be able to install graphp/graphviz package too !

[clue]

@llaville Good catch, will make sure this is updated across the @graphp organization once this PR is merged! GitHub automatically sets up redirects for old branch names, so I think the previous installations should continue to work in either case.

[llaville]

GitHub automatically sets up redirects for old branch names, so I think the previous installations should continue to work in either case.

@clue No it does not works when you add constraint on version with alias into a composer.json file like that :

    "require": {
        "php": "^7.4.0 || ^8.0",
        "graphp/graph": "1.x-dev#41e73a5 as 1.0.0",
        "graphp/graphviz": "dev-master#42a2098 as 1.0.0"
    },

Composer 2.4 prints

  Problem 1
    - Root composer.json requires graphp/graphviz dev-master#42a2098 as 1.0.0 -> satisfiable by graphp/graphviz[dev-master].
    - graphp/graphviz dev-master requires graphp/graph dev-master#214de45 as 1.0.0 -> found graphp/graph[dev-master] but it conflicts with your root composer.json require (1.x-dev#41e73a5 as 1.0.0).

So, please apply change on graphviz package ASAP !

[clue]

@llaville See graphp/graphviz#64.

I hope this helps! 👍 If so, consider supporting this project, for example by becoming a sponsor ❤️