Proto commits in tikv/agatedb

These 4 commits are when the Protocol Buffers files have changed:

Commit:dbfc35e
Author:Alex Chi
Committer:GitHub

table: prepare for adding table impl (#19) * fix typo of Comparator * use little endian in header * use little endian when encoding offset * use big endian in builder length Signed-off-by: Alex Chi <iskyzh@gmail.com>

The documentation is generated from this commit.

Commit:67b2284
Author:Alex Chi
Committer:GitHub

complete table builder (#13) Signed-off-by: Alex Chi <iskyzh@gmail.com> Co-authored-by: Jay <BusyJay@users.noreply.github.com>

Commit:fc497f1
Author:Alex Chi
Committer:GitHub

switch to prost (#5) * use prost Signed-off-by: Alex Chi <iskyzh@gmail.com> * fix format Signed-off-by: Alex Chi <iskyzh@gmail.com>

Commit:920fc60
Author:Jay Lee

partial implement