Update docs

[erikyo]

In this PR we are going to update

• Readme replaces require (cjs) with import (esm), adds installation instruction
• package.json - update package info
• CHANGELOG.md - annotate changes before release the new version

[johnhooks]

@erikyo are you going to use this PR to update all the package.json details too? Like converting it to @wp-blocks/gettext-parser? And do we want to save v1.0.0 for after the TS rewrite?

[erikyo]

nope, because to publish the package on npm we have to change the name and the rest of the info... good catch, I'll add this as a part of this PR