README: Add Cocoapods link

[natikgadzhi]

This PR adds a README entry on how to install SwiftLog with CocoaPods. Closes #75

Motivation:

I'm honestly just learning Swift and open source Swift tooling by browsing repositories and trying things out. If I see an issue that I can close in a few minuites that nobody got to yet — cool!

I doubt many people still use CocoaPods, but hey. I did test that the snippet works in an example project locally.

Modifications:

Added a paragraph in README.md about Cocoapods.

Heads up: at the time of this PR, the current pod version is 1.4, and the current SwiftPM version available is 1.5.2. Time to regenerate the podspec again?

/cc @weissi, seems like this is your area?

[ktoso]

Thank you for the PR and thank you for spending the time on it!

Sorry but I don't think we actually support cocoapods at all. I'm not even familiar with how publishing for them works, so can't say for sure -- but we certainly don't maintain anything related to it.

[ktoso]

cc @tomerd @weissi @Lukasa

[natikgadzhi]

Looks like there’s 1.4 spec pushed up to cocoa pods, but I agree that it’s not quite a priority. No hard feelings, good to close!

[0xTim]

Related - Cocoapods has been dropped across all the server-side and related libraries. See https://forums.swift.org/t/swiftnio-is-dropping-support-for-cocoapods/56840

[natikgadzhi]

@0xTim, woooops. Thank you for the link!

Seeing the feedback, and how other libraries (drop) support for Cocoapods, I don't think we should introduce the paragraph in the README as I've written it. So, closing this PR.

If anything, perhaps we should clean out the podspec tooling across this and other libraries. Since they're not in the way, I think that's a pretty low priority. Happy to be a janitor if you need a full repo-by-repo sweep, though.

/cc @ktoso, @weissi, @tomerd.

[ktoso]

Ah thanks for bringing up that link @0xTim !

Thanks @natikgadzhi !