fix: underscore escape while html transforming

[ChengShi-1]

What this PR does / why we need it:

Fix the bug that the underscore are escaped with backslashes and accumulate.
After investigating, the function transformHtmlToMarkdown leads the underscore format problem, for example, input: "test_" would be transformed to "test\_". This error isn't followed with other symbols, only underscore.

After I give an underscore to the title, the test information looks like this

Which issue(s) this PR closes:

• Closes underscores are escaped strangely with backslashes and accumulate #241

Special notes for your reviewer:

Suggestions on how to test this:

Even though this is a js-dataverse repo PR, the test has to be done on front end SPA page.
Environment Setting: in package.json, change to "@iqss/dataverse-client-javascript": "v2.0.0-pr242.cbb959e", runnpm i, and run npm run build, may need restart docker as well.

1. create a dataset, give a title, subtitle or email(any text area) with underscore _, such as [email protected]
2. edit the dataset metadata randomly, but keep the underscore
3. check the information display in the dataset page, underscore should be there without any strangely backslash.

[ekraffmiller]

Closing this because it will be addressed by IQSS/dataverse-frontend#588