docs: simplify README.md

[LukeWinikates]

• move releasing instructions into their own file
• remove table discussing SDKs not in this repo
• remove examples in README in favor of code examples
• add internal SDK metrics to this README

[LukeWinikates]

see #106

[keep94]

It seems you are removing all the SDK examples from the readme documentation. I believe this is the direction we want to go, but I don't remember seeing example code in your other PR for histograms for instance.

[keep94]

Someone from our tech writing team should have a look at this PR since it involves changes to the README file. I am figuring out who that person will be.

[LukeWinikates]

It seems you are removing all the SDK examples from the readme documentation. I believe this is the direction we want to go, but I don't remember seeing example code in your other PR for histograms for instance.

Thanks Travis - yep, this PR removes the examples from the README. It looks like I did convert all of the readme examples into godoc examples, so spans, histograms, metrics, and delta counters are all included in the test file added by this PR.

[keep94]

LGTM

[shavidissa]

Hi Team,

Question: Why are we removing the section on how to send data and configure. (how will a user know how to do these. Can we document the content so it's clear to users) :)

[keep94]

Hi shavidissa, we are planning to move all the example code over to pkg.go.dev and add a link to pkg.go.dev from the readme. For you to see the changes on pkg.go.dev, we'd have to do a release, but if you download the godoc tool on your machine and checkout this PR, you can get a fairly accurate preview of what the page on pkg.go.dev will look like. I can show you how to do this if you'd like.

[shavidissa]

Thank you for the explanation! I have a few minor comments.
LGTM after the changes are made :)

[LukeWinikates]

thanks @shavidissa!

@keep94 I also created #118 as a place to discuss whether we can make the RELEASING.md steps easier.

[LukeWinikates]

@keep94 do you think we're ok to merge this PR now? I think all the review comments are resolved