Add LSTM and softmax to operators.md (#2346)

* Add LSTM and softmax to operators.md

* Fix lowercase and support_inplace

docs/developer-guide/operators.md

@@ -7,6 +7,8 @@
 * [concat](#concat)
 * [convolution](#convolution)
 * [dequantize](#dequantize)
+* [lstm](#lstm)
+* [softmax](#softmax)
 
 # absval
 ```
@@ -133,3 +135,32 @@ y = activation(x3, act_type, act_params)
 |1|bias_term|int|0|
 |2|bias_data_size|int|0|
 
+# lstm
+Apply a single-layer LSTM to a feature sequence of `T` timesteps. The input blob shape is `[w=input_size, h=T]` and the output blob shape is `[w=num_output, h=T]`.
+
+* one_blob_only
+
+|param id|name|type|default|description|
+|--|--|--|--|--|
+|0|num_output|int|0|hidden size of output|
+|1|weight_data_size|int|0|total size of IFOG weight matrix|
+|2|direction|int|0|0=forward, 1=reverse, 2=bidirectional|
+
+|weight|type|shape|description|
+|--|--|--|--|--|--|
+|weight_xc_data|float|`[w=input_size, h=num_output * 4, c=num_directions]`||
+|bias_c_data|float|`[w=num_output, h=4, c=num_directions]`||
+|weight_hc_data|float|`[w=num_output, h=num_output * 4, c=num_directions]`||
+
+# softmax
+```
+softmax(x, axis)
+```
+
+* one_blob_only
+* support_inplace
+
+|param id|name|type|default|description|
+|--|--|--|--|--|
+|0|axis|int|0||
+|1|fixbug0|int|0|hack for bug fix, should be 1|