feat: Add run-doc subcommand to run the test and generate markdown docs

[zikani03]

This changeset adds a new sub-command named run-doc which can be used to generate markdown from the steps in the .basi file as a way to aid in documenting steps for applications in addition to testing them.

This is very early and very experimental, lot's of things to figure out. But it works okay enough for a first pass,

Usage:

$ basi run-doc example-hn.basi

You will get a markdown with the following (Screenshots are added between each step and referenced in the markdown ):

# Test Document for  

Documented by Basi

1. Goto https://news.ycombinator.com/login

![[Figure 2]](./step-0.png)

2. Fill input[name=acct]

![[Figure 3]](./step-1.png)

3. Fill input[name=pw]

![[Figure 4]](./step-2.png)

4. Click input[value=login]

![[Figure 5]](./step-3.png)

![[Figure 5]](./test-screenshot.png)