[Ready - 2] FileSystem: Text Stream

[satviksr]

I have created the FileStream object to have a similar design as used by the FileIO module. This allows us to easily reuse the FileIO helper functions.

• [ ] Handle open files locking correctly

Implement

• [x] isEndOfLine
• [x] isEndOfStream
• [x] getColumn
• [x] getLine
• [x] read
• [x] readAll
• [x] readLine
• [x] skip
• [x] skipLine
• [x] write
• [x] writeLine
• [x] writeBlankLines
• [x] close

Test

• [x] isEndOfLine
• [x] isEndOfStream
• [x] getColumn
• [x] getLine
• [x] read
• [x] readAll
• [x] readLine
• [x] skip
• [x] skipLine
• [x] write
• [x] writeLine
• [x] writeBlankLines
• [x] close

Update: I plan to handle file locking of open files in a different PR, I have raised an issue for the same #63

[todo[bot]]

Implement in memory same process - File Locking

VBA doesn't allow 2 files to be opened for writing at the same time.

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https://github.com/googleinterns/filesystem-in-appsscript/blob/1068449d1c616b765172d09f2c18e33709141cc7/FileSystem/VbaTextStream.js#L24-L29

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This comment was generated by todo based on a todo comment in 1068449d1c616b765172d09f2c18e33709141cc7 in #48. cc @googleinterns.