add fusetools gitignore

[tim-hub]

Reasons for making this change:
Fuse is a developing frame for mobile application development, and I think adding this gitignore will help the new developers. ^_^

Links to documentation supporting these rule changes:

https://www.fusetools.com/learn/fuse#

If this is a new template:

• Link to application or project’s homepage: https://www.fusetools.com

[eeue56]

New link confirming this: https://www.fusetools.com/docs/getting-started/getting-started#git

[knatten]

LGTM! I've been working in Fuse for many years, and this matches what we currently use.

(The build directory used to be called .build back in the days, but that gets deleted every time you clean your build anyway, so I'd prefer to just have build and .uno like in this PR.)

[shiftkey]

I'm going to close this out because I'm not sure of the overall value of maintaining this template in the repository.

@tim-hub if you feel like this should still be a template listed in the repository, please read the section about specialized templates and open a new pull request targeting the new location.