tqdm: add examples

[BuonOmo]

• The page(s) are in the correct platform directories: common, linux, osx, windows, sunos, android, etc.
• The page(s) have at most 8 examples.
• The page description(s) have links to documentation or a homepage.
• The page(s) follow the content guidelines.
• The page(s) follow the style guide.
• The PR title conforms to the recommended templates.
• Version of the command being documented (if known): v4.67.1

[tldr-bot]

The build for this PR failed with the following error(s):

pages/common/tqdm.md:
Error: Parse error on line 16:
...dm --bytes --total `du -sb {{{docs/}} | 
-----------------------^
Expecting 'NEWLINE', 'TEXT', 'DASH', 'BACKTICK', got 'COMMAND_TEXT'
pages/common/tqdm.md:15: TLDR021 Command example should not begin or end in whitespace

Please fix the error(s) and push again.

[acuteenvy]

Suggested change

	- Show iterations per second and use stdout afterwards:
	- Show iterations per second and use `stdout` afterwards:

[acuteenvy]

This example doesn't work very well. The du command will output the size of the docs directory, but the size of a gzip-compressed tarball will be smaller than that, and so the progress bar will stop when it reaches the size of the compressed archive instead of 100%.

Here's the final output after compressing some files:

93%|██████████████████████████████▉           | 33.1M/35.4M [00:01<00:00, 31.1MB/s]

[BuonOmo]

Would you prefer that one ? Also taken from the docs.

7z a -bd -r backup.7z docs/ | grep Compressing | \
    tqdm --total $(find docs/ -type f | wc -l) --unit files >> backup.log