Merge branch 'fix-normalisation-cases' into 'master'

__tests__/files/gmail-gmail/one/20/s_plainContent.data

__tests__/files/gmail-outlook/one/02/r_htmlContent.html

__tests__/files/gmail-outlook/one/02/s_htmlContent.html

__tests__/html-gmail-gmail.test.ts

__tests__/html-gmail-outlook.test.ts

__tests__/html-outlook-outlook.test.ts

__tests__/plain-gmail-gmail.test.ts

__tests__/utils.ts

src/HTMLNormalizer/strategies/gmail.ts

src/HTMLNormalizer/strategies/nodesAmendingFunctions.ts

src/HTMLNormalizer/strategies/outlook.ts