Fix some typos and update one example

[sbraz]

Type of changes

• [ ] Bug fix
• [ ] New feature
• [x] Documentation / docstrings
• [ ] Tests
• [ ] Other

Checklist

• [x] I've run the latest black with default args on new code.
• [x] I've updated CHANGELOG.md and CONTRIBUTORS.md where appropriate.
• [x] I've added tests for new code.
• [x] I accept that @willmcgugan may be pedantic in the code review.

Description

Hi, just some tiny fixes I noticed while reading the doc. Thanks for maintaining rich, it's great :)

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Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.23%. Comparing base (310defc) to head (2edbc66). Report is 29 commits behind head on master.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #3452 +/- ## ======================================= Coverage 98.23% 98.23% ======================================= Files 74 74 Lines 8060 8060 ======================================= Hits 7918 7918 Misses 142 142 ``` | [Flag](https://app.codecov.io/gh/Textualize/rich/pull/3452/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/Textualize/rich/pull/3452/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None) | `98.23% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=None#carryforward-flags-in-the-pull-request-comment) to find out more.

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