Woofmark upgrades, Custom insert module, and many more improvements

This release incorporates a LOT of fixes as well as some new features. It builds on #557 however we have bumped up to v2.2.0 as there are new features included. Thanks to @NitinBhasneria @shreyaa-sharmaa @Shulammite-Aso @keshav234156 @sagarpreet-chadha @emilyashley and others for bringing things this far!!! Congrats, folks!

Published on NPM as well: https://www.npmjs.com/package/publiclab-editor

Now moving to merge into plots2 at: publiclab/plots2#8297

Fixes

1. Popup Disappearing problem solved by @NitinBhasneria jywarren/woofmark#3
2. Feature to change heading back into plain text by @shreyaa-sharmaa jywarren/woofmark#5
3. Refine drag and drop events to prevent interference by @NitinBhasneria jywarren/woofmark#2
4. fix bold texts loosing formatting after converting to markdown and back to wysiwyg by @Shulammite-Aso jywarren/woofmark#15

Features

1. Added custom insert module by @keshav234156 #568
2. ADDS: Feature to decenter text in wysiwyg and markdown modes by @Shreyaa-s #521
3. Add support for class attributes in links by @Shulammite-Aso #547
4. Compact design for Main Image Module by @shreyaa-sharmaa #594

Changes

1. Repoint woofmark to pull in fixes from latest plots2 branch of woofmark, https://github.com/jywarren/woofmark/tree/plots2
2. Includes jest-puppeteer tests in woofmark by @Shulammite-Aso jywarren/woofmark#11
3. Made history icons consistent in demo editor fixes by @Shulammite-Aso #571
4. Main image box padding and background improvements by @NitinBhasneria #564
5. "Remove file" button test added by @NitinBhasneria #574
6. Redefines puppeteer as a dev dependency by @Shreyaa-s #565
7. Update dependencies in woofmark on plots2 branch by @Shulammite-Aso jywarren/woofmark#17