Fix broken tables whose msgstr is a specific type of HTML

[shinmili]

If an msgstr for a table cell contains HTML that could be parsed as an HTML block if it were put in the top-level, the table is rendered incorrectly. The table row containing the cell gets interrupted in the middle and split into two (or more, if there are more such cells) incomplete rows.

Close #251.

[google-cla[bot]]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 98.82353% with 1 line in your changes missing coverage. Please review.

Project coverage is 86.05%. Comparing base (886f15e) to head (9b96374). Report is 16 commits behind head on main.

Files with missing lines	Patch %	Lines
i18n-helpers/src/lib.rs	97.77%	0 Missing and 1 partial :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #253      +/-   ##
==========================================
+ Coverage   84.74%   86.05%   +1.30%     
==========================================
  Files          15       17       +2     
  Lines        3377     3750     +373     
  Branches     3377     3750     +373     
==========================================
+ Hits         2862     3227     +365     
- Misses        413      419       +6     
- Partials      102      104       +2     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

:rocket: New features to boost your workflow:

• :snowflake: Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[mgeisler]

Hi @shinmili, thank you so much for putting this up! I think this looks good and I left some minor comments.