Moving SRAM docs from gf180mcu-pdk

[mohanad0mohamed]

• Moved all documentations in docs directory.

• Made symbolic link for it in gf180mcu-pdk

• Built locally with no errors

Fixes google/gf180mcu-pdk#11

[mithro]

I have reworked this pull request slightly. I move the specs to a specs directory under each cell. See the commit at 894afa5

[mithro]

@mohanad0mohamed - I have updated this pull request for you.

[mohanad0mohamed]

Thanks @mithro. I was going to do the same but I didn't know that I can put directories inside each cell.
I thought this shouldn't happen so I made them in docs directory.

[mohanad0mohamed]

I have moved code_of_conduct.rst and contributing.rst outside docs not to produce warnings. Also edited README.rst to change 180um to 180nm.

I think this edit should happen also in mcu7t5v0 and mcu9t5v0 not to produce warnings in building the docs.

[mithro]

I have moved code_of_conduct.rst and contributing.rst outside docs not to produce warnings. Also edited README.rst to change 180um to 180nm.

Two comments;

• Please keep pull requests to a single item.
• We should fix the warnings from these docs, not remove the docs all together.

[mithro]

@mohanad0mohamed - I have removed the non-moving SRAM docs changes from this pull request.