feat: bash input signs are no more parts of copy btn content

[bolotskydev]

Describe changes
This commit makes sure terminal input signs are no more parts of copy btn content in code blocks.

Verbose

Unfortunately, I failed to set up attaching $ signs automatically as planned initially for two reasons:

1. First try: attach to every single line of a bash code block

Quickly realised it was a bad idea since bash blocks may include not only bash commands, but output as well and $ signs would be redundant and look weird.

2. Second try: use the only possible way to distinguish terminal input from terminal output programmatically.

Lines with input starts with function token type whereas output tokens have token type of plain. I set up to attach $ sign to a beginning of a code line if it starts with function, but It turned out this isn't an option as well: prism parser doesn't recognize such commands as brew, docker, k6 etc, so lines starting with those wouldn't have $ sign and we have no capabilities to extend the dictionary.

Given that, I came up with the following solution: we keep $ signs in bash terminals, add them manually where we need it, but copy button would be stripped of every $ that is a first character of a code line.

Side:

• adjusted CodeGroup component similarly how it was done on blog to prevent buggy behavior
• added $ signs to bash blocks on Installation page

Steps to test

1. Open up preview, find any bash terminal with $ signs indicating the bash input
2. Click on Copy button, paste the buffer content
3. Assure $ chars were stripped from lines indeed

References
Closes #158

[github-actions]

There's a version of the docs published here:

https://mdr-ci.staging.k6.io/docs/refs/pull/161/merge

It will be deleted automatically in 30 days.

[simskij]

Ace! Good job!