[Snyk] Upgrade gatsby-theme-carbon from 1.27.0 to 1.29.0

Snyk has created this PR to upgrade gatsby-theme-carbon from 1.27.0 to 1.29.0.

merge advice :information_source: Keep your dependencies up-to-date. This makes it easier to fix existing vulnerabilities and to more quickly identify and fix newly disclosed vulnerabilities when they affect your project.

The recommended version is 5 versions ahead of your current version.
The recommended version was released a month ago, on 2021-04-19.

The recommended version fixes:

Severity	Issue	PriorityScore (*)	Exploit Maturity
	Arbitrary Code Injection SNYK-JS-EJS-1049328	312/1000 Why? Proof of Concept exploit, CVSS 4.1	Proof of Concept

(*) Note that the real score may have changed since the PR was raised.

Release notes

Package name: gatsby-theme-carbon

1.29.0 - 2021-04-19
1.29.0 (2021-04-19)

Features
- adding workplace design into switcher (#1117) (c6d755e)
1.28.0 - 2021-04-01
1.28.0 (2021-04-01)

Features
- date in frontmatter resolves last modifed date on page (#1094) (17947ce)
Bug Fixes
- adjust search container width to align with page contents (#1105) (c08db04), closes #1101
- update latest carbon and add style override for sidenav overlay bug (#1106) (7f4378e)
- update package.json scripts for npm users (#1103) (d855fac)
- zindex for search bar on headernav style (#1096) (5b81985)
1.27.3 - 2021-01-22
1.27.3 (2021-01-22)

Bug Fixes
- 404 link color and config branch as main (#1085) (659ea89)
- added Racial Equity to switcher -closes #1057 (#1088) (c1e18fd)
- fail gracefully without page titles (#1065) (aeba5ea)
1.27.2 - 2021-01-06
1.27.2 (2021-01-06)

Bug Fixes
- un-minify homepage image to remove jank (#1071) (cef5a5c)
- global search: 1989-aat-avt1-gs-about-carbon-aria-expanded (#1064) (7520c0b)
- header link fix (#1076) (1252373)
- header nav refactoring (#1044) (c9384a0)
1.27.1 - 2020-11-23
1.27.1 (2020-11-23)

Bug Fixes
- page-tabs: nav aria unique labels (#1063) (a536b8a)
- default exports (68594c5)
- feedback and back to top button mobile spacing (#1052) (db91ffd)
- footer: width of rules on mobile (#1051) (aa7d34a)
- search: update search styles (#1050) (bcc3f23)
- ordered list styles in firefox (#1047) (eae9688)
1.27.0 - 2020-10-22
1.27.0 (2020-10-22)

Features
- Aside: add option to hide hanging rule from Aside component (#1014) (d416901)
- Theming: Adds Dark, White, and g10 themes to GTC (#979) (432f243)
- update switcher content (#1023) (ed2df93)