Add changesets (#4154)

* add first changesets integration

* remove readme

* readd readme

* update auto-release workflow logic

* update auto-release script order, fix prettier

* change access to public

* update release script

* try to fix changesets

* add experimental snapshot version config

* try fixing

* remove excess

* switch auto-release branch to master

* add release pull request workflow

* add changeset todo to pr template

* update changeset

.changeset/README.md

@@ -0,0 +1,8 @@
+# Changesets
+
+Hello and welcome! This folder has been automatically generated by `@changesets/cli`, a build tool that works
+with multi-package repos, or single-package repos to help you version and publish your code. You can
+find the full documentation for it [in our repository](https://github.com/changesets/changesets)
+
+We have a quick list of common questions to get you started engaging with this project in
+[our documentation](https://github.com/changesets/changesets/blob/master/docs/common-questions.md)

.changeset/config.json

@@ -0,0 +1,13 @@
+{
+  "$schema": "https://unpkg.com/@changesets/config@1.5.0/schema.json",
+  "changelog": "@changesets/cli/changelog",
+  "commit": false,
+  "linked": [["slate", "slate-history", "slate-hyperscript", "slate-react"]],
+  "access": "public",
+  "baseBranch": "master",
+  "updateInternalDependencies": "patch",
+  "ignore": [],
+  "___experimentalUnsafeOptions_WILL_CHANGE_IN_PATCH": {
+    "useCalculatedVersionForSnapshots": true
+  }
+}

.changeset/lovely-rats-suffer.md

@@ -0,0 +1,8 @@
+---
+'slate': patch
+'slate-history': patch
+'slate-hyperscript': patch
+'slate-react': patch
+---
+
+**Start using [🦋 Changesets](https://github.com/atlassian/changesets) to manage releases.** Going forward, whenever a pull request is made that fixes or adds functionality to Slate, it will need to be accompanied by a changset Markdown file describing the change. These files will be automatically used in the release process when bump the versions of Slate and compiling the changelog.