message: Make emphasis style consistent
diff: [Search the existing issues](https://github.com/tradingview/lightweight-charts/search?type=Issues) before logging a new one.
  -*Don't* restrict your search to only open issues. An issue with a title similar to yours may have been closed as a duplicate of one with a less-findable title.
  +_Don't_ restrict your search to only open issues. An issue with a title similar to yours may have been closed as a duplicate of one with a less-findable title.
  ### Filing an Issue
  When logging a bug, please be sure to include the following:
  - What version of the library you're using.
  -- If at all possible, an *isolated way* to reproduce the behavior.
  +- If at all possible, an _isolated way_ to reproduce the behavior.
  - The behavior you expect to see, and the actual behavior (e.g. screenshots).
  - Make sure the issue title is understandable and searchable.
  