Add support for character after jira project key

[agitelzon]

I can see that there are 2 old PRs in this repo to do essentially the same thing. Please take a look at these PRs and implement something similar to what both are trying to do.

Right now this action will only support the format <JIRA-ISSUE-KEY> <Title> with a space between the key and PR title, for example, AB-123 PR Title.

We would love it if this action, at minimum, could support AB-123: PR Title or at best custom separators such as:

<JIRA-ISSUE>:<Title>
<JIRA-ISSUE>_<Title>
<JIRA-ISSUE>-<Title>
<JIRA-ISSUE>/<Title>