SVN Batch file output linebreaks and formatting - powershell

Question

I am creating a simple 'post-commit' svn batch script, which will run when a member of our development team commits a build. This batch file sends off the resulting output to a slack service which spits it out to our team channel.
This all works without any problems, but I'd like to put in some bespoke formatting such as new lines and maybe bold text. It's a bit hard to read at present. Being able to break to a new line is the main thing that I'm after. I've done a lot of searching, but can't seem to find the correct answer.
Does anyone have experience with this?
Here's the contents of my script currently:
set one=%1
set rev=%2
set changes=svnlook changed %one% -r %rev%
set whatchanged=nothing
for /f "delims=" %%a in ('%changes%') do ( set whatchanged=%%a )
for /f "delims=-" %%i in ('%rev%') do (
SET rev=%%i
)
for /f "delims=" %%g in ('svnlook log %one% -r %rev%') do (
SET comlog=%%g
)
for /f "delims=" %%i in ('svnlook author %one% -r %rev%') do (
SET "author=%%i"
)
for /f "delims=" %%i in ('svnlook changed %one% -r %rev%') do (
SET changed=%%i
)
powershell -Command "& Invoke-RestMethod -Uri 'our URL with a unique token goes here' -Method Post -Body (ConvertTo-Json #{text='%author% %rev% %one% %comlog% %whatchanged%'})"
REM All checks passed, so allow the commit.
exit 0
The output currently looks like this:
liam.mcdonald 171 D:\Repositories\company
Here is another one:
U Test/New Text Document.txt