[PTRun][UnitConverter]Add usage prompt

[NaroZeol]

Summary of the Pull Request

Added usage prompt when a keyword is typed

PR Checklist

• Closes: [PowerToys Run] Increase User-Friendliness of PTRun Unit Converter Plugin #34575
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated
• New binaries: Added on the required places
  • JSON for signing for new binaries
  • WXS for installer for new binaries and localization folder
  • YML for CI pipeline for new test projects
  • YML for signed pipeline
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Added usage prompt when a keyword is typed

I'm not sure whether this usage prompt is enough. I tried adding the supported units, but the input box is too narrow to display them all. Any feedback welcomes

[htcfreek]

Wondering if we show possible conversation if we know the first query part.

%% 10 ft to shows:

%% 10 ft to m
%% 10 ft to km
.....

[NaroZeol]

Wondering if we show possible conversation if we know the first query part.

%% 10 ft to shows:

%% 10 ft to m
%% 10 ft to km
.....

Well, why not just show the results if you show so many prompts.

%% 10 ft shows:

304.8 cm
3.048 m
0.003048 km
........

It sounds great, but it's not a part of this PR.

We can do this in another one!