handle uris from browsers

[pazos]

Or any app that states android.intent.category.BROWSABLE on their intents.

Restricted to file and content schemes from any host.

Also added a filter by extension, in case the sending app is nuts (I never needed it here but I see it is commonly used)

Also added markdown to the list.

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This change is 

[Frenzie]

Also added a filter by extension, in case the sending app is nuts (I never needed it here but I see it is commonly used)

I'm not sure if I entirely understand, but alright. :-)

[pazos]

Also added a filter by extension, in case the sending app is nuts (I never needed it here but I see it is commonly used)

I'm not sure if I entirely understand, but alright. :-)

The system will register KOReader MainActivity as an option to open given content if, for whatever reason, that content fails to match any of the supported mimetypes but still has one of the supported extensions.

[Frenzie]

I see, that makes sense.