Dependency instant is unmaintained

[akatsukilevi]

According to the RUSTSEC-2024-0384:

This crate is no longer maintained, and the author recommends using the maintained web-time crate instead.

This affects the web-push library since it is a peer-dependency in the chain:

Crate:     instant
Version:   0.1.13
Warning:   unmaintained
Title:     `instant` is unmaintained
Date:      2024-09-01
ID:        RUSTSEC-2024-0384
URL:       https://rustsec.org/advisories/RUSTSEC-2024-0384
Dependency tree:
instant 0.1.13
└── fastrand 1.9.0
    └── futures-lite 1.13.0
        ├── web-push 0.10.2
        │   └── mocha_hub 0.0.1
        └── isahc 1.7.2
            └── web-push 0.10.2

One possible solution could be upgrading the isahc dependency to the latest stable version (1.7.2 as of the time of writing), opposed to the 1.4.0 currently in use