chore(changelog): Add script to generate release notes

This PR adds documentation and a script for maintainers to use to automatically generate release note content from GitHub Pull Requests.

Flags

Note that the mapping in package.json uses the lowercase version of the GitHub Labels with unicode emoji characters rather than their short-codes.

Here is a sample output for the latest unreleased changes.

ui-contract-editor
- #277 style(ui-contract-editor): Drag-Drop Handle Resize - I137 (@K-Kumar-01)
- #250 feat(ui-contract-editor):drag&drop disabled for embeded clauses (@sanketshevkar)
storybook, ui-components, ui-concerto, ui-contract-editor, ui-markdown-editor
- #247 feat(package): add repository information to package.json (@Aniruddha-Shriwant)
ui-markdown-editor
- #237 feat(ui-markdown-editor): center align h1 tags - I146 (@Udbhavbisarya23)
- #225 style(ui-markdown-editor): remove link modal fade-in effect - I218 (@K-Kumar-01)
storybook, ui-markdown-editor
- #229 style(ui-markdown-editor): resolve toolbar icon shrinkage - I228 (@K-Kumar-01)

ui-markdown-editor
- #283 fix(ui-markdown-editor): styleblock refresh - #276 (@d-e-v-esh)
- #268 bug(ui-contract-editor): remove z-index of toolbar - I87 (@Udbhavbisarya23)
- #252 fix(ui-markdown-editor):multi-para to list proper indent - I158 (@K-Kumar-01)
- #258 fix(ui-markdown-editor): list formatting is preserved in headings (@gatij10)
- #222 fix(ui-markdown-editor): resolve hyperlink overflow - I219 (@K-Kumar-01)
ui-contract-editor
- #251 fix(ui-contract-editor): Highlight read-only text clause template - i242 (@K-Kumar-01)
- #240 fix(ui-contract-editor) prevent sig variable edits on readOnly - I212 (@sanketshevkar)
- #231 fix(ui-contract-editor): prevent clause drag and drop in list - I157 (@sanketshevkar)
- #236 fix(ui-contract-editor): adjust tooltip z-index - I185 (@K-Kumar-01)
ui-components
- Long clause template names intersect with template logo (@Michael-Grover)

storybook, ui-concerto
- #273 feat(ui-concerto): Upgrade to Concerto v1.0 (@mttrbrts)