Added function to get Rich Texts from blocks

[wulfharth7]

I've opened a PR for the #165 but the initial PR became a mess. These are my first contributions so whenever I fix something, I usually rush and the commit history gets messy because of my excitement :D

Anyways, I wanted to fix that so I've opened a new branch to create a new PR with a better history.

[jomei]

@wulfharth7 build failed, please take a look

[wulfharth7]

@wulfharth7 build failed, please take a look

Interesting. I have the solution. So basically when I transform these functions from these

func (p *ParagraphBlock) GetRichTextString() string {
	return concatenateRichText(p.Paragraph.RichText)
}

func (h *Heading2Block) GetRichTextString() string {
	return concatenateRichText(h.Heading2.RichText)
}

to these

func (p ParagraphBlock) GetRichTextString() string {
	return concatenateRichText(p.Paragraph.RichText)
}

func (h Heading2Block) GetRichTextString() string {
	return concatenateRichText(h.Heading2.RichText)
}

It passes the build tests. Do you have any ideas why is that so? I've cloned my first commit on the first PR and tested it. Turns out it also fails the tests (even though github didn't say so).

I've checked the block_test.go on the lines 95-128. Thats the place where it gives the error for these 2 functions. I'll check further but I need your thoughts on this topic as why it happens. Or why could that happen?

I could just transform the functions, push the commit and the functions would start working without any build errors as I've shown in the screenshots on my first PR.

But before that I just wanted to ask why, do you have any clues?

I can just do the changes and push though @jomei

[jomei]

@wulfharth7 To be honest there's no specific reason to use value receiver instead of pointer one..
So let's change to value receivers here and may be change to pointers everywhere in a separate PR later.

[wulfharth7]

@jomei Done. This time it should pass the tests as I've checked. I'll check further for this pointer thing later when I have time.