Improve help search matching

[chiizujin]

Brief overview of PR changes/additions

If help entries have similar names, it may be impossible to access one or more of them. This change fixes that, resolving #3532.

Motivation for adding to Evennia

Improvement/bug fix.

Other info

This seems to be related to lunr and is further complicated by the fact that commands can be prefixed with "@".

In the case of "test" and "tests", lunr ranks both of these the same, no matter which is searched for:

help test
{'ref': 'test', 'score': 44.819, 'match_data': <MatchData "test">}
{'ref': 'tests', 'score': 44.819, 'match_data': <MatchData "test">}

help tests
{'ref': 'test', 'score': 44.819, 'match_data': <MatchData "test">}
{'ref': 'tests', 'score': 44.819, 'match_data': <MatchData "test">}

I don't know if this PR is the most elegant fix but I couldn't find any lunr-based solution.

Examples

Before:

>help test
Help for test
(...)
Other topic suggestions:
tests

>help tests
Help for test
(...)
Other topic suggestions:
tests

>help spawn
Help for spawns
(...)
Other topic suggestions:
spawn

>help spawns
No help found

There is no help topic matching 'spawns'.
... But matches were found within the help texts of the suggestions below.

Other topic suggestions:
spawn  spawns

Example from the bug report:

>help interactions
Help for interact
(...)
Other topic suggestions:
interactions

>help interact
Help for interact
(...)
Other topic suggestions:
interactions

After:

>help test
Help for test
(...)
Other topic suggestions:
tests

>help tests
Help for tests
(...)
Other topic suggestions:
test

>help spawn
-------------------------------------------------------------------------------------
Help for spawn (aliases: olc)
(...)
Other topic suggestions:
spawns

>help spawns
-------------------------------------------------------------------------------------
Help for spawns
(...)
Other topic suggestions:
spawn

>help interact
Help for interact
(...)
Other topic suggestions:
interactions

>help interactions
Help for interactions
(...)
Other topic suggestions:
interact