MM-19964 Properly handle whitespace before code block language

[hmhealey]

Our fork of marked incorrectly didn't trim the whitespace before the language tag in a code block, which the PR below fixes

Ticket Link

https://mattermost.atlassian.net/browse/MM-19964

Related Pull Requests

Marked PR: mattermost/marked#16

[saturninoabril]

Tested and passed.

[saturninoabril]

💯

[amyblais]

@hmhealey Please help merge this PR before the end of your day today.

[mattermod]

@hmhealey
Error trying doing the automated Cherry picking. Please do this manually

+++ Updating remotes...
Fetching upstream
Fetching origin
+++ Updating remotes done...
+++ Creating local branch automated-cherry-pick-of-#4186-upstream-release-5.17-1573661879
Branch 'automated-cherry-pick-of-#4186-upstream-release-5.17-1573661879' set up to track remote branch 'release-5.17' from 'upstream'.
+++ Downloading patch to /tmp/4186.patch (in case you need to do this again)

+++ About to attempt cherry pick of PR. To reattempt:
  $ git am -3 /tmp/4186.patch

Applying: MM-19964 Properly handle whitespace before code block language
Using index info to reconstruct a base tree...
M	package-lock.json
M	package.json
Falling back to patching base and 3-way merge...
Auto-merging package.json
CONFLICT (content): Merge conflict in package.json
Auto-merging package-lock.json
CONFLICT (content): Merge conflict in package-lock.json
Patch failed at 0001 MM-19964 Properly handle whitespace before code block language
Use 'git am --show-current-patch' to see the failed patch
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

+++ Conflicts detected:

UU package-lock.json
UU package.json

+++ Aborting in-progress git am.

+++ Returning you to the master branch and cleaning up.