Update Readme & Provide current context on Hardware Acceleration on Github (#279)

* Clarify README with mid-2022 updates, and add info for spellchecker to action.yml

* Remove redundant paragraph in Usage section, and add relevant links to intro paragraphs

* Add HAXM installation example and remove linux emphasis

* Remove gist which contained manual emulator creation/startup

* Add clarity to GPU vs VM acceleration in README

* Fix reversal of examples in README

* Add support for commenting run tests on PRs to rerun checks if they fail

* Add better conditional logic to determine if comment is issue or PR

.github/workflows/main.yml

@@ -1,5 +1,6 @@
 name: Main workflow
 on:
+  workflow_call:
   pull_request:
     paths-ignore:
       - '**.md'

.github/workflows/pr-comment.yml

@@ -0,0 +1,9 @@
+name: Re-Run Tests on PR Comment Workflow
+on:
+  issue_comment:
+    types: [created]
+  
+jobs:
+  rerun-tests-job:
+    if: github.event.issue.pull_request && contains(github.event.comment.body, 'run tests') # if comment is created on a PR, can also use the syntax if: contains(github.event.comment.html_url, '/pull/')
+    uses: ./.github/workflows/main.yml