Better documentation of the add-on translation process

[seanbudd]

Our current resource for translating add-ons on the wiki is out of date and refers to pages explaining SVN/PoEdit that have been removed in favour of Crowdin.
It would be great to create documentation in this repository which covers the translation process for add-ons, not just the registration process.
Using the archives of the previous pages might be useful, but most content was out of date.

[nvdaes]

I think that @BlindHelp may be interested in this issue and eventually provide feedback.
I'm in charge of add-ons registration for translations, and I thought that add-ons would use svn, not Crowdin.
If the system is changing, this may be producing issues with notifications submitted to translators when add-ons documentation needs to be updated.
cc: @michaelDCurran.

[seanbudd]

@nvdaes - sorry my original message may have been unclear.
NV Access has removed all documentation on using SVN as we use crowdin now.
As a result, there is no documentation on how to translate add-ons.
I think it would be helpful to add documentation on how to translate add-ons to this repository.

[nvdaes]

Sean wrote:

I think it would be helpful to add documentation on how to translate add-ons to this repository.

I agree. Now I understand your comment.

[nvdaes]

Imo the centralized system is useful and almost not used. I'm not a translator, and writing documentation is not one of my better skills.
Perhaps some translators are interested in this. Otherwise I may try to work on this, but usually I write in a very concise style and hope someone can work on this.
cc: @CyrilleB79