Add tag for embbedable stuff, and non pure ones

[bizulk]

Recently I consulted libcdada lib for manipulating containers, it links on the stdc++.
I expected this list to have no dependy to C++, as said in the awesome readme page, to justify its living with the "awesome c++" page. But it appears that c++ backend entries are alloyed. I can understand this as we can compile pure C code with the g++ project.

But Maybe we could add a tag for those entries.
Morevover I'm interested to identify a subset of the list as an "embbedable" stuff : "microcontroler" are getting more powerful but still have a lot of limitation to code that must be embbeded in 2 Mo Max memory. And very often the build project is not easily adapted for this type of processor.

For more powerful target as ARM application processor, I do not consider them : now they embbed a lot of memory, and the only difficulty is about cross-compilation.

Finally resolving #155 prior to this issue would help.