Integrate prettier to the project and ci and prettify project

[matux]

Description of the change

This PR enables formatting checks in the CI with prettier and formats the entire project, including library, examples, tests, config files, html and markdown.

The following HTML errors identified by prettier were fixed as well:

examples/error.html
[error] examples/error.html: SyntaxError: Unexpected closing tag "html". It may happen when the tag has already been closed by another tag. For more info see https://www.w3.org/TR/html5/syntax.html#closing-elements-that-have-implied-end-tags (49:1)
[error]   47 |   <button id="throw-depp-stack-error" onclick="throwDeepStackError(0,20)">Throw deep stack Error</button>
[error]   48 |   <button id="throw-event-handler-error" onclick="throwEventHandlerError(0,20)">Throw event handler Error</button>
[error] > 49 | </html>
[error]      | ^^^^^^^
[error]   50 |

examples/include_custom_object.html
[error] examples/include_custom_object.html: SyntaxError: Opening tag "a" not terminated. (39:18)
[error]   37 |     <button onclick="window.myvariable = {foo: 'bar'}; Rollbar.info('test from include_custom_object.html');">Send test message, myvariable = {foo: 'bar'}</button>
[error]   38 |     <br><br>
[error] > 39 |     See results: <a href="https://rollbar.com/Rollbar/rollbar.js/items/420/?item_page=0&#instances">rollbar/rollbar.js#420</a>
[error]      |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[error]   40 |
[error]   41 |   </body>
[error]   42 | </html>

examples/webpack/src/index.html
[error] examples/webpack/src/index.html: SyntaxError: Unexpected closing tag "html". It may happen when the tag has already been closed by another tag. For more info see https://www.w3.org/TR/html5/syntax.html#closing-elements-that-have-implied-end-tags (22:1)
[error]   20 |   <button id="rollbar-info-with-extra" onclick="rollbarInfoWithExtra()">Log info and store JSON payload</button>
[error]   21 |   <button id="send-json" onclick="sendJson()">Send stored JSON</button>
[error] > 22 | </html>
[error]      | ^^^^^^^
[error]   23 |

Type of change

• [ ] Bug fix (non-breaking change that fixes an issue)
• [ ] New feature (non-breaking change that adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [x] Maintenance
• [ ] New release

Checklists

Development

• [x] Lint rules pass locally
• [x] The code changed/added as part of this pull request has been covered with tests
• [x] All tests related to the changed code pass in development

Code review

• [x] This pull request has a descriptive title and information useful to a reviewer. There may be a screenshot or screencast attached
• [ ] "Ready for review" label attached to the PR and reviewers assigned
• [ ] Issue from task tracker has a link to this pull request
• [ ] Changes have been reviewed by at least one other engineer