Improved README & CHANGELOG

[tisba]

I Fixed some typos and other nit-picky whitespace stuff in CHANGELOG.

I made a bit more changes to the README. I actually wanted to fix some typos and move the troubleshooting up based on issues opened by users having trouble installing mini_racer, but then I guess I got carried away and tried to make some more improvements 😁

• fixed various typos, inconsistencies and extra whitespace
• I added a rubygem version "badge", because I saw quite a few bug reports not on the latest version, maybe this helps 🤞
• I also moved the troubleshooting section up quite a bit, also in hopes that this helps to minimize reported bugs, that are easily fixed by using the troubleshooting guide 🤞🤞
• fixed a formatting error I added in Add note on Windows support to README #268 🤦
• the memory soft limit example was broken. A non-existing print() was called, but it wasn't needed to showcase the feature anyway so I just dropped that
• in the examples, I switched to ECMAScript's Template Literals to show that mini_racer actually supports modern JS.
• I tried to add links to various things mentioned, like to the docs on how to load memory profiles into Chrome DevTools, etc.

Please let me know if that's too much in one go and I can split this up for easier review.

[SamSaffron]

this looks good to me!

odd that truffle is failing atm @eregon ?

[eregon]

https://github.com/rubyjs/mini_racer/actions/runs/5083216358/jobs/9133946519
Thanks for the ping. It seems it tries to compile libv8-node instead of using the precompiled gem as intended (because it doesn't need it anyway). Maybe some issue in Bundler, I'll try to repro locally.

BTW rubyjs/libv8-node@abae20e would fix this but mini_racer imports an older version of libv8-node.

[eregon]

Yes, it's simply ruby/rubygems#6165, I'll try to use a newer Bundler to avoid this issue.