vdoc: highlight inline examples for `-f html`
This doesn't include multi-line examples or README.md example.
Part of https://github.com/vlang/v/issues/13851.
If the example isn't valid V:
```v
// Example: `if ouch { return error('an error occurred') }`
```
You'll get an error like:
```
internal_memory:1:47: error: invalid character literal `if ouch { return error('an error occurred') }` => `if ouch { return error('an error occurred') }` ([`i`, `f`, ` `, `o`, `u`, `c`, `h`, ` `, `{`, ` `, `r`, `e`, `t`, `u`, `r`, `n`, ` `, `e`, `r`, `r`, `o`, `r`, `(`, `'`, `a`, `n`, ` `, `e`, `r`, `r`, `o`, `r`, ` `, `o`, `c`, `c`, `u`, `r`, `r`, `e`, `d`, `'`, `)`, ` `, `}`]) (more than one character)
internal_memory:1:1: details: use quotes for strings, backticks for characters
```
This one is less informative about the source line:
```v
// Example: assert 'h`.is_capital() == false
```
```
internal_memory:1:33: error: unfinished string literal
```
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