convert html to flat text for LHN uses

[mollfpr]

@parasharrajat @Luke9389 will you please review this?

[Explanation of the change or anything fishy that is going on]
I'm adding a new function to replace the HTML report message that use for showing text on LHN.

Fixed Issues

$ Expensify/App#8134

Tests

1. What unit/integration tests cover your change? What autoQA tests cover your change?
   __tests__/ExpensiMark-FlatText-test.js
2. What tests did you perform that validates your changed worked?

> Confusing stuff
Tell me about it

Type above text and should be converted to text Confusing stuff Tell me about it

QA

1. What does QA need to do to validate your changes?
   Verify that __tests__/ExpensiMark-FlatText-test.js is pass.
2. What areas to they need to test for regressions?
   The function created is used on showing the converted html last message on LHN.

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[mollfpr]

I have read the CLA Document and I hereby sign the CLA

[mollfpr]

recheck

[parasharrajat]

Shouldn't this be updated?

[mollfpr]

Ahh yeah forgot about that, I'm on it.

[mollfpr]

Any things I should update here?

[parasharrajat]

cc: @Luke9389

[Luke9389]

I'm surprised the tests with blockquotes work, considering that the

const html = '<blockquote>Confusing stuff</blockquote>Tell me about it';
const text = 'Confusing stuff Tell me about it';

Why isn't there a space before the word "Confusing" here?

[Luke9389]

Also, it seems we're only capturing the closing tag. I must be wrong about that though because the tests are passing.

[mollfpr]

Why isn't there a space before the word "Confusing" here?

Also, it seems we're only capturing the closing tag. I must be wrong about that though because the tests are passing.

Here we loop the 3 rules

1. replacing breakline with space /((<br[^>]*>)+)/gi
2. replacing blockquote with space /<\/blockquote>/gm. This the solution for the issue
3. strip all the tags left behind with an empty string /(<([^>]+)>)/gi

        this.htmlToTextRules.forEach((rule) => {
            replacedText = replacedText.replace(rule.regex, rule.replacement);
        });

@parasharrajat @Luke9389

[Luke9389]

Ahh, ok, I see. I didn't realize we apply all rules in a row.

thanks for the explanation!

[s77rt]

This PR caused a bug Expensify/App#17658. The html to text function should have also unescaped html entities e.g. < to <.