Add Laravel 9 support

[gbuckingham89]

Laravel 9 is due for release on February 8th.

I've had a look through the upgrade guide (in its current state - obviously won't be finalised until the release) and I don't think there are any breaking changes that will cause problems in this package.

Therefore this PR simply adds ^9.0 to the version constraints in composer.json for the illuminate/* dependencies.

We'll also need the bosnadev/database dependency to add ^9.0 support, so I've opened a similar PR there.

[ajthinking]

Hi @gbuckingham89 , thanks for this! Im also looking forward to Laravel 9 support.
Until we can have it here, I published a fork: https://github.com/ajthinking/laravel-postgis which seems to work.
Like you said bosnadev also needs bumping, and it somewhat slumbering, so those parts needed is now merged into the above fork repo.

Maintainers, please let me know if I can help add the fork updates in here instead 🙏

[patricknomad]

I upgraded my app from Laravel 8 to Laravel 9 and @ajthinking's solution works great for me.

[mstaack]

lets go 🚀

[nabilelmahiri]

Hello, Laravel 9 support not working in the last commit 5.3 because of bosnadev/database needs bumping, we either need to bump it up or go for @ajthinking solution !

Problem 1
- bosnadev/database[0.21, ..., 0.21.1] require illuminate/database ^5.0|^6.0|^7.0|^8.0 -> found illuminate/database[v5.0.0, ..., 5.8.x-dev, v6.0.0, ..., 6.x-dev, v7.0.0, ..., 7.x-dev, v8.0.0, ..., 8.x-dev] but these were not loaded, likely because it conflicts with another require.
- mstaack/laravel-postgis 5.3 requires bosnadev/database ^0.21 -> satisfiable by bosnadev/database[0.21, 0.21.1].
- Root composer.json requires mstaack/laravel-postgis ^5.3 -> satisfiable by mstaack/laravel-postgis[5.3].

[mstaack]

sure please open a fixing PR, will merge then